I second the turnip gratin. There is another delicious one (with carrots and dill) in Marian Morash's Victory Garden Cookbook, which is back in print, thank goodness. And brussels sprouts: no fancy prep, just done to taste in a big pot of boiling water, then buttered. With all the rich stuff at Thanksgiving, a simple green thing is just right. Last thought: the easy and delicious chard gratin in Alice Waters's Simple Cooking.

PPS - shred the turnips!!

I make a root gratin every year that people just love. Judith Olney has a turnip gratin recipe that I have tweaked: 6 or 7 cups of turnips and rutabagas (or just turnips like the original recipe) salted, drained, and wrung of all liquid; sauteed in 4 TBLS. butter for 10 minutes; and placed in a buttered gratin dish. Pour about 2/3 to one cup Half and Half over them, pepper, and sprinkle some fresh bread crumbs over the top (I use crumbled Ritz crackers). Dot with a little butter and bake in a 375-degree oven for 30 minutes. It is delicious!!

This is refreshing, a nice alternative to the usual heavy Thanksgiving fare..

Saute sliced carrots in olive oil. Add in some crushed garlic and cumin, salt and pepper (you can use cayenne if you want.). Stop cooking it before it gets mushy! Then add lemon juice and some chopped herbs -- either parsley, mint or cilantro or a mix. Tastes good warm, room temperature or cold.

You can play around with the seasonings too, maybe coriander instead of/ in addition to cumin, etc

Melt butter in a saucepan, throw in some thyme sprigs until they pop and the butter starts to turn green.

Pour the butter over carrots, stir or toss to coat, and sprinkle with salt, pepper, and thyme leaves.

Roast in the oven at 375 until you get some decent browning going on. Make sure you spread the carrots out as much as possible, or you won't get much browning.

Barley pilaf is a great sub for potato dishes. Melt a stick of butter in a big skillet, and saute a large onion and 2 cups pearled barley. Add a half-cup slivered almonds, a cup of sliced mushrooms, 2 5-ounce cans of water chestnuts, drained and chopped, 2 minced garlic cloves, salt and pepper, celery salt, and 4 cups chicken broth. Pour into a greased casserole dish and bake for an hour at 350; top it with a mix of bread crumbs and parmesan and return to oven until top is golden.

Two of my favorites are:

1. Brussels sprouts -- Prepared any number of ways -- raw, roasted, gratin, etc.

2. Roasted carrots & beets -- Gorgeous colors and easy to prepare -- just peel and cut into smallish pieces, toss with olive oil and kosher salt and roast at 400 degrees until nicely browned. Reheats especially well so you can prepare them in advance.

You all are fabulous. These sound so great! Since there are 25 people coming for Thanksgiving, I might make 2 or 3 of these. Thanks!

For something different and fun, try this savory pear and red onion gratin - it's unexpected and completely delicious - I've served it many times for Thanksgiving

http://www.eatingwell.com/recipes/pear_red_onion_gratin.html

i love making gratins-- spinach, brussels sprouts, eggplant. they're fairly easy to assemble, and they can be as rich or as light as you want them to be. i also like the idea of a plate of simply roasted vegetables, like carrots, beans, and broccoli, seasoned simply with salt, pepper, olive oil, and a splash of lemon juice or white vinegar.

Roasted root vegetables (sweet potatoes, parsnips, carrots, turnips) peeled and cut into similar size pieces. Toss in olive oil. Sprinkle generously with a mix of ground cumin, fennel seeds, coriander seeds, smoked paprika, salt and pepper. Roast at 400 degrees until caramelized. I'd add fennel and whole cloves of peeled garlic.

stuffed artichokes!

I'm down with brussels sprouts also. Instead of the usual preparation you might think about slicing them very, very thin. Saute them in butter (go ahead throw some chopped bacon in there), season with salt and pepper. Just get them to color. Add a bit of water,cover and steam for a few minutes. Finish with a splash or two of tarragon vinegar. The good thing about this preparation is that it can be made in fairly large batchs.

melissa clark's raw broccoli salad -- spicy and delicious.
http://query.nytimes.com/gst/fullpage.html?res=9800E6DE1031F933A15751C0A96E9C8B63&scp=1&sq=broccoli%20salad%20clark&st=cse

I had a quick version of this for dinner, tossed with apple cider vinegar, olive oil and agave nectar. http://www.food52.com/recipes/1710_brussels_sprout_salad_take_2

I can't stand cooked brussels sprouts, but love it raw.

We like sauerkraut as a counterpoint to all the rich (and creamy) sides. I caramelize some onions, add the kraut and some caraway seed, a tbsp of brown sugar and about 1/4 cup of turkey juices or stock and heat it through. It's a nice contrast to everything else on the table, yet still rather traditional in some communities.

I love a savory squash or pumpkin side dish. These two are both fabulous- I've made them both in the last two weeks.
A butternut squash savory bread pudding:
http://www.ezrapoundcake.com/archives/10067
Dorie Greenspan's Pumpkins stuffed with bread, cheese, and bacon. If you omit the bacon, it could also double as a vegetarian entree. It is so, so good. http://www.epicurious.com/recipes/food/views/Pumpkin-Stuffed-with-Everything-Good-361169
like @Sadass_ulna, I'm a huge fan of brussel sprouts. Here is a rundown of some great brussel sprout recipes. http://www.thekitchn.com/thekitchn/recipe-roundup/green-globes-of-goodness-12-recipes-for-brussels-sprouts-lovers-130377
This winter panzanella is so fresh and delicious. I like to shave the brussel sprouts instead of cooking them for some added crunch.
http://smittenkitchen.com/2006/12/holding-the-gray-salt/

I dislike the 'regular' sweet potatoes and have used this as alternative. Cube and barely parboil sweet potatoes. Drain very well. Saute 'til lightly caramelized with a chopped onion and red bell peppers. Throw in a bag (or more depending on your quantity) of frozen sweet corn kernels. Season with cumin, salt & pepper. Top with cashews.

Clean a head of cauliflower. Boil the entact head for about ten minutes. Drain. Spread a good brown mustard all over it. Then coat with grated cheese. Bake on a greased baking sheet at 350 degrees until golden. That should take about 30 minutes. A mix of cheeses like yellow Cheddar, asiago, and parmeasan works nicely.

How about some pan roasted brussel sprouts? There are lots of great looking recipes here on food52.

Alton Brown's carrots cooked and glazed in ginger ale and butter, which also works for sweet potatoes.

Raw broccoli, cauliflower and cherry tomatoes in a garlic vinaigrette--colorful and crunchy, unlike everything else on the table.

Roasted green and wax beans--toss beans with a few dribbles of olive oil, sprinkle with McCormick Montreal steak seasoning, put in the oven at 425 degrees for about 20 minutes or until beans begin to caramelize.

Creamed peas and carrots. Creamed cipollini or pearl onion gratin. Creamed peas and pearl onions. Corn Pudding. Which reminds me--there are some beautiful and simple corn recipes in Amanda's book, "The Essential NY Times Cook Book."

I second the greens idea. Last Thanksgiving, I sauteed two bunches of broccoli rabe in olive oil and garlic at the last minute, only because everything on my menu seemed so.. monochromatic. Everyone ended up really liking the bitter counterpart to all the richness.

Any grating would be nice and easy. Butternut squash gratin either made with carmelized onions and broth or with cream and gruyere cheese would be nice. Swiss chard or spinach gratin with a little cram and parmesan would provide greens.

Oh and another thing I do every year (mostly because my sister in law would beat me if I stopped) is make a cream cheese parmesan artichoke spinach dip and bake it in a hollowed out pie pumpkin - then when you are scooping out the dip you get some nice cooked pumpkin bits too - serve it with some crostini and everyone gets a nice little bread and spread treat on their plate. That's sort of a veggie ... with cheese ...

Hmm - ok well last TDay I made a mess o greens mostly for my mother in law but everyone went crazy for them - I fried up some bacon lardon and onions, then added a BUNCH of greens (25 people!) I used kale, collards, and mustard greens - and added some broth to help them cook down. Taste and add salt and pepper as needed and then I add pepper vinegar - which is just a spicy vinegar and you could certainly skip the spicy bit and just add some white wine vinegar ... or add some chopped jalapenos or serranos.