Kaplan's Online Q-Bank (www.kaptest.com) has been a staple of USMLE Step 1 prep for many medical students. Usually, during the month before the exam, students study for 8 hours during the day, and then they take a few hours to take the 2,000+ questions available online.
Online Web Prep provides a few hundred lectures based on subjects. A 9 month subscription is available from Kaplan for a reduced price at medical schools. Its a good way to learn during the actual class itself, and review related materials. The Web Prep comes along with Kaplan's lecture notes books.