I have found recently very interesting site, hosted by publisher of Lodish et al. "Molecular Cell Biology" 6th edition.
2020 update: link is dead now
For this blog's purpose most interesting part of that service are Online Quizzes. Nice feature there is that it is possible to subscribe your instructor to your results.
Other services are lots of animations, tutorials, review and more-more stuff. I would like to mention here "Classic Experiments" section of the site.
What is even more exciting is that there are similar sites for 5th and 4th editions users! And there is GRE kind test on site dedicated to the 5th edition.
I really admire those people, who maintain biological education services online and on such high level. I think it is dangerous lack of opportunities for online reviewing, testing and upgrading knowledge in russian bio education.