I use Quia to make online multiple choice tests.  Since my lab is kitted out with 12 tablet Pcs I can  use these for testing in class. ( This saves me having to mark them and record the marks :-)) They are primarily for use by the students as a revision aid.

 There are over 1000 questions, each time you open the test you get a random 15.  

Now with FEEDBACK

If you get a question wrong you get feedback to tell you how to do it.  As you can imagine this took a long time to set up but now its done I hope it proves useful.