The best way to get started with Lisp is PLT Scheme, from Northwestern. You might also read their free book, How to Design Programs. IU's computer science department is a center of Scheme development and research, so there is a good chance classes will use Scheme.
Note: Lisp is an old language, old enough to have fragmented into dialects. The principle surviving dialects are Scheme and Common Lisp (which was a sort of koinonia at the time of its creation). Scheme has strong academic roots and so tends to have more pedagogical material available.
There are several experimental dialects at any given time. Two are Clojure and Arc. They are more appropriate if you want to use Lisp for writing real-world code.