Depends what you are looking for. If it's medical literature you are looking for, you can't beat medline. If your school doesn't have access to medline, I'd recc emedicine.com and medscape.com as 2 strong free resources. My med school pays for mdconsult, but I can't stand it. We pay a lot for mdconsult, but uptodate.com is much better. Uptodate is expensive, but so is mdconsult.