4tests.com: Offers 60 free multiple choice USMLE questions.

Active Learning Center: An interactive site that allows you to create your own exam from categories of drugs.  Setting your own test length, deciding what classes of drugs to be tested on, and keeping track of your score are all features.

Histology World: This site contains free review questions, atlases, and links.

NetPharmacology: This site contains lecture notes, drug lists, and test questions with annotated answers for cardiovascular pharmacology.

Pharmacology Final Exam: A medical pharmacology exam with answers at the bottom of the page.

Free Practice Tests: Self-assessment modules for behavior science, biochemistry, circulation, diabetes, gastrointestinal, gross anatomy, integumentary, lymphatic system, neuroanatomy, nutrition, pathology, pharmacology 1 & 2, physiology, reproduction, respiration, syndromes, and urinary system.

Pharmaco Jeopardy (Antibiotics):  Interactive Jeopardy format with questions pertaining to antibiotics.

Pharmaco Jeopardy (cancer chemotherapy):Interactive Jeopardy format with questions pertaining to Cancer Chemo.

Pharmaco Jeopardy (Pulmonary and GI): Interactive Jeopardy format with questions pertaining to Pulmonary and GI drugs.

Physiology Review Study Questions:  Study questions in the areas of GI, Cardio, and Respiratory.

Quia - Flashcards - Anatomic Directions - Body Positions: This site uses the flashcard format to help learn the introductory concepts of anatomical direction and body positions.