I lived there until 2005, so you can PM me if you like for specifics.
Your entertainment options are as follows:
Downtown Urbana: has a few townie bars, one in particular where the MBA and JD students play darts (a bit more mainstream), a decent (for Chambana) thai restaurant and organic supermarket. Classification-still pretty townie and dead. Urbana sure is pretty though, I lived there for 2 out of 3 years.
Downtown Champaign: older crowd than option 3 (described below)-mostly graduate students and the profs. There’s a martini bar, a sports bar, an artsy theatre and quite a few restaurants. I’d recommend Radio Maria to eat. It’s like Champaign’s version of upscale dining that is non-chain.
Green Street: alongside Date Rape Row…umm, basically this is where all the undergrads go to booze. Several very cheap Chinese, korean, greek/middle eastern, pizza etc. restaurants and skeezy disgusting bars where I’m still convinced they recycle the remnants of people’s beer. On the other hand, it has 1 of the only 2 Indian restaurants in town. Every freaking Indian seems to send their kid to UIUC but there are only 2 restaurants in town and I think the one on Green Street is slightly better if only because they’re polite and hire local kids to serve you.
Outer Champaign: movie theatre, walmart, target and several chain stores. You need a car to get here. I can’t imagine why you’d want to go unless you have a burning desire to eat at Chili’s and watch a movie.
Scattered: there are neat places around campus-ish. There are two nice restaurants alongside the new administration building (kind of like Radio Maria but I believe both are Italian).
Things to do: you can wander around campus, check out the “test patch” and the architecture, I guess.
For the size of the university…the whole C-U scene is kind of small. It’s not an Ann Arbor or Madison by any means. On the other hand, their non-profit radio station, WPGU is still one of my faves, and is a pretty good resource for things to do. I think I like it even better than the glory days of WFNX 101.7 in Boston. You can also pick up the weeklies and the campus newspaper for events going on in terms of concerts and whatnot (the only time I’ve ever seen Ravi Shankar live was at UIUC).
Also, my old classmate still lives in the area and writes an awesome blog called Central Illinois Life. She’s a really cool chick-feel free to email her for better/more details and say Anu/Monkey referred you (or you can just leave her a blog comment or something). You can filter out her C-U posts with the tags on the right side of the blog.
Hope that helps.