you should look through the 'official medicine shelf thread' under 'clinical rotations' section.
i would recommend that you finish step up to medicine, and then if you have time start doing some questions. everybody loves casefiles, blueprints or pretest but if you're shooting for >80, you should do:
1. Harrison's Principles of Internal Medicine Board Review (you can either buy the book or do questions via accessmedicine.com [if your school has institutional subscription])
2. IM section (8 blocks of 50 questions) in Kaplan Step 2 CK Qbook
Good Luck