Good, and hot, gravy is the secret to the turkey. It can come out of the oven early and will keep a fair bit of heat for a fair while (just don't stuff it, OK?), it really doesn't matter since once you carve it it goes cold quickly anyway. Keep your gravy hot and replenish often!

I love all of these suggestions! I baked homemade bread in my neighbor's oven last Thanksgiving (with their permission of course) while they were away. I agree with AntoniaJames about the microwave being questionable for some things, but dishes like sweet potatoes could be made the day before and heated/served in a microwave-proof dish. As for refrigerator space, I have used my car as a second fridge when the weather here in Pennsylvania was on my side ;) I really like kjrmcclain's suggestion of using coolers to keep things warm.

If your guests like turkey breast, what about making an additional turkey breast the day before or early in am?? I also find my biggest challenge is fridge space. You might also consider getting a third rack for your oven if you don't have one - won't help while turkey is roasting but will help with heating up sides. Also, lots of sides taste good room temp - grain salads, roasted veggies, etc.

You can easily grill a turkey, but I suggest doing so in pieces rather than whole, you get a much more evenly cooked bird. it's also a lot easier to carve and doesn't take up as much space in the oven if you have to keep it warm for a while.
Pies are almost always better the next day, make them the night before and tent the top with foil to keep condensation from dripping on the crust. You can fill cream pies early in the day and just keep them chilled, pre-bake the crusts and make the filling the night before.
Of course, you could always ask your guests to each bring a side dish. It provides some really interesting diversity and then you only have to worry about keeping things warm. We've done this since I was a small child and it's never been a problem. Thanksgiving dinner is generally 60+ people or so, so it's probably just a matter of necessity.
Otherwise, simplify. Only make two sides, only make one kind of pie, and buy some good bread.

These are all great ideas, from everyone . . . one other suggestion re logistics . . . . take all your serving dishes out the night before, and put the serving utensil you'll use for each one in it, along with the name of the dish to go in there, written on a 3 x 5 card, with any reminders that may be pertinent. Also, post a master list of everything you plan to serve somewhere that is very visible, and actually check off each item as it leaves the kitchen or other pre-dinner area, and goes into the dining room. I've had more than one T-Day when I've left a relish or chutney -- typically something I made during the summer or earlier in the fall, and brought up to the kitchen from my long-term pantry the weekend before -- that simply didn't make it out to the sideboard or the table to enjoy with the meal. Of course, each was enjoyed with leftovers the next day, but you get my point. ;o)

The good old days, when all the kids and their friends were home, and I didn't have those dang pesky in-laws (the other grandparents) that I now have to share my sons (and their kids) with. . .oops. Sorry for venting here.

I used to roast one turkey in the oven (a Butterball for its drippings) and grill one outside on a natural-gas grill (a brined and spatchcocked fresh turkey directly on the grates, a drip pan underneath). I've never been able to do a killer turkey on charcoal, so I quit trying, but other people's success stories are making me reconsider. That, plus my gas grill died and it with a middle-of-the-line Weber.

Here's a couple of ways to maximize your oven's availability:

Prep and bake as much as you can the days and nights before, or the very early morning of, Thanksgiving.
On Monday, make pie dough, roll it out, fit it into pie plates, wrap in plastic and freeze. (You can stack them once they've frozen solid.) Thursday morning, mix your pumpkin and pecan fillings and bake the pies, which will make the house smell heavenly while you prep the stuffing and the turkey.
Tuesday, make the dough for crescent rolls, let it go through the first rise, punch it down, divide it and flatten into two 2"-thick discs, wrap in plastic and freeze. Take the dough out of the freezer when the turkey goes in the oven, let thaw, then shape crescents and let them go through a second rise. Put them in the oven while the turkey is resting. Stir the gravy, mash the potatoes, and when the rolls have just begun to brown, turn the oven off and prop the door open 1" with a folded potholder. The rolls will finish baking while you carve the turkey.

You can keep two racks in the oven if you spatchcock your turkey and cook the stuffing/dressing in a separate pan, or if you roast a small whole turkey and a whole bone-in, skin-on turkey breast.

If you do sweet potatoes, you can roast them directly on the rack, fitting them between whatever pans are in the oven. If space allows, you might be able to fit a small rack, such as one on which you cool cookies and cakes, on the floor of the oven, for the sweet potatoes. Wrap them in foil--they have a habit of oozing caramelized juice and setting off smoke detectors.

My first Thanksgiving was a logistical nightmare. I insisted on making everything and instead of holding food, I wanted to finish it all at the last minute. It all worked out, but it was very difficult. I had cooked for 25+ before, but the menu was easier to manage. I few tricks that learned and now live by:

Every dish has a home. When I host something large, I create a menu matrix that dictates where items need to be at a given time. This helps me to not forget that one last thing I was supposed to do, allows me to actually know when I can step away to visit, and gives everyone to talk about because I actually created a project matrix for my meal.

I use all of my resources. My toaster oven is a convection version that allows me to warm appetizers on two racks concurrently. I typically use a cooler to store all the 13x9 casseroles until they are ready to go into the over since I do not have enough room in my refrigerator. My regular oven (also convection) has room for me to cook 3 13x9 casseroles (stuffing/dressing, etc) while my turkey is resting and being broken down. My microwave came with 2 extra racks which help keep up to 3 additional 13x9 casseroles up to temp while other items are cooking. I do not use it for anything else. As far as the turkey is concerned, when done it will rest comfortably in a large cooler. I The cooler is almost as effective at keeping things warm as it does keeping them cool. If you prep mashed potatoes beforehand, their thermal mass helps keep everything toasty in the cooler as well. The smoked turkey (grill) is good, so if you go that way you have a simpler job since your oven is now free.

Staging is everything. Just like the actual cooking itself, having all my tools at the ready and all of the mess out of the way is key. Although I do not have difficulty seating 25, my kitchen is just not designed to be a small restaurant. I set up two tables in my garage (near my kitchen). One table is for everything I will need throughout the day of cooking and the other is for the dirty stuff that I do not have time to deal with once the festivities start. I also run short on refrigerator space, so the garage end up being a convenient location to keep perishable items and desserts until needed (I live in the Northeast). I also prep a trash can with a heavy duty trash bag that I can use instead of my little kitchen trash can and waste disposal. Lastly, I have all of my containers and storage bags at the ready for cleanup.

Without knowing exactly what dishes you have in mind, I'd just make these general suggestions. First, you'll want to map out, very specifically, on a daily calendar page (i.e., by the quarter hour) what's going to made/finished/reheated when, and where. Obviously, you should choose as many side dishes and desserts as possible that can be made ahead. Include on your timetable exactly when each pre-made or pre-prepped item is to come out of the refrigerator, to bring to room temperature. Second, remember that the turkey will need to rest for at least a half an hour. The minute the turkey comes out, the dishes that need to be finished in the oven, or reheated, can go in. Make all of your pies the night before, or early on T-Day, but make sure you frame or tent the crusts, because you don't want them too dark if you plan to warm them in the oven. Consider whether any dessert item could actually cook in the oven after the sides are out, while you're eating dinner. Many sides can be made while the turkey is cooking, but look for every way possible to do advance prep. E.g., caramelized onions, which might used to start a dish, hold really well in the fridge for a couple of days. As for your microwave, use it for heating broths, melting butter, etc., but don't rely on it for actually making or heating an entire dish unless and until you've test driven the actual recipe, in the quantity that you plan to serve. Results can vary dramatically, and the last thing you want is a chewy overcooked crust on the outside of a dish with a cold interior. Finally, and probably most important, delegate! Is someone who is attending (and who is very reliable) willing to work with you to contribute? Would they be willing to cook something in their oven (that you made and gave them the day before, or from a recipe that you agreed to, or from a recipe you've provided) and bring it? Sounds like exactly the kind of challenge I love, just about more than anything else I do in the kitchen! Good luck!!

Have you thought about deep-frying the turkey? Here's a primer from wiki-how:
http://www.wikihow.com/Deep-Fry-a-Turkey