Scrubs is definately up there although the last couple seasons have been a bit hit or miss on the episodes but that happens to every show. I get pissed at the Comedy Central ones because they chop out like 5 minutes worth, and what gets chopped are usually my favorite scenes.
I'm surprised noone has mentioned The Office, that also comes back tonight, whee! Also anyone watch How I Met Your Mother? Thats a pretty funny show. Oh, and I always make sure to watch Boston Legal.