The Lincoln Trail Library system is well-designed, and if the Champaign Pub Lib doesn't have what you need, they'll find a way to connect you with someone that has the book or whatever material you want/need. Also, they have a rather fantastic collection of CDs. This is a great place to study on a quiet afternoon, but also near finals, it can be a nice place to escape from campus and your apartment. It's also wonderful to be there when working on a paper or project where a seemingly endless number of resources are needed. Big tables are great for spreading out.
All of this said, be careful because they are rather strict about which library you've got a card to (it all depends on where you live) and they are also a little strict about cleanliness, etc. Lots of money was spent on this library, though, so I believe it's warranted.
Also: WiFi is free, but only if you have a library card. Not sure how it works if you do not have a library card.