Thanks everyone for your help!

This is what I ended up doing: I cooked penne until about 2 minutes to al dente. I drained the pasta and put it into ziploc bags, drizzled some olive oil into the bag and sealed them. I kept them wrapped in towels until dinner time. Someone brought me a HUGE crockpot, so I could put all the pasta in it with a little reserved pasta water and keep it warm until serving. The pasta, sauce and meatballs were a big hit.

I am sorry it took me so long to reply, so thank you for your amazing suggestions!

I'm with iuzzini, casserole and baked dishes stay hot longest. Still watch your times and temps for safety. Kaybe has a great suggestion. I often have to negotiate this as I cook for a crowd everymonth with no kitchen. I wish the OP would report back

Can you turn it into a baked ziti/rigatoni type of dish? Then you can bring it hot and it will still be tasty when as it cools down . . . you can chop the meatballs into it, or serve them on the side in a crock pot . . .

From many years of the First Assembly of God Spaghetti Dinner (one of the social events of the season in the small town where I previously lived) -- toss the cooked pasta with a few tablespoons of olive oil, and then with a cup or two of whatever sauce you're using (minus the meat). That will keep the noodles from clumping together in the chafing dish, or, more to the point, the big roasters the ladies of the 1stAG used to serve it from.

If it's going to be a buffet-style potluck with lots of different foods, I'd use a chafing dish. Get the water in the chafer nice and hot. Then before placing your just-cooked pasta into it, put out the flame underneath. This way, you'll just have the ambient heat from the hot water warming the food.

Also, you might want to think about cooking your pasta a tiny bit less than al dente, as it will continue to cook no matter how you end up keeping it warm.

If the meatballs and sauce are in the crockpot, you could also try to just run the noodles under very hot water or get a big bowl/pot, put pasta in and cover pasta (from a hot water urn if you can plug something like that in) with boiling water. Then drain.

Just Have everything already on the table and at the last minute do betteraines suggestion. Have pasta already cooked and lightly oiled so that it won't stick and at the last minute drop it in a simmering pot for a minute and then drain and serve. it would take two minutes and the moment you set the cook pasta on the table dinner is ready. I usually mix sauce with the noodles and put on a warmed platter and top with more sauce and garnish (cheese, basil or oregono) and set on the table. stays warm enough even for seconds.

I've never tried this, but this is what my experience and cooking "instincts" tell me. Pick a pasta shape like penne or fusilli and cook them just al dente (so they are still just a bit hard). Drain them well, toss them with a bit of good olive oil, and refrigerate them. Before the party, put them in a crockpot with the lid on it -- and WITHOUT the sauce -- for about an hour on low, just to get them warm. Right before serving, and I mean immediately before, i.e., when people are standing at the serving table with their plates in their hands, mix the well-heated sauce and meatballs (which you've gotten real hot, again using a crockpot on the high setting) with the warmed pasta. Good luck!!!

What about a chafing dish?

I haven't found a good way to keep pasta warm, especially spaghetti, without it sticking together or worse, becoming mush. How will you be keeping the sauce hot? It sounds as if your best bet would be to add the noodles to the hot sauce at the very last minute.

When I was a line cook many, many years ago, we'd halfway cook a couple of pounds of spaghetti at a time, drain and cool it, then wrap each portion in plastic and refrigerate it. When an order came in, we'd throw a portion into the pot of simmering water kept on a back burner. You could fill a crock pot or other electric cooking appliance with hot water and do something similar, but this probably wouldn't make for easy, efficient or quick serving.