I know at my school (University of South Florida), previous students put together a list and describe which books were necessary, which were optional, and which were completely useless. Second years are paired-up with first years, and sometimes you can "borrow" or receive as a gift some of the books that the second years used during their first year.
I'm one of those people who likes to buy the books that I feel will be useful in the future and because I like to have my own books at the ready when I want to study. I feel it's a good investment for me, but many others do not. I've kept some of my undergrad books (Clinical Neuroanatomy, Pathophysiology, Rhones Color Atlas of Anatomy, Junqueira Histology, Netter's Atlas of Anatomy, etc) because they will be useful in medical school. I plan on buying all of the student-recommended books (and not the useless ones as advised by the students), but will extensively use half.com, Amazon, and other online stores to cut costs. I will only use the student bookstore for the impossible to find books and to just browse.