I discovered a new site today that is following in the mold of "jailbreaking" knowledge and making it available for the world to access similar to Khan Academy or Learn Zillion. Gnowledge is a little different though in that is is purely the assessment piece without the videos and the instruction. I took an assessment on Earth Materials and found it very easy to use and quick to submit. I like the feedback at the end and the ability to distinguish myself to the author if I was a student for a grade. Gnowledge is a great site for creating more than just assessments but also homework assignments and quick checks in progress (e.g. after completing a reading in class or at home). Using Gnowledge to create a quiz was very simple and the ability to track your assessment scores is a really cool feature for students. Students can also take assessments created by other teachers which is an excellent way for them to practice previously learned skills.
If you are looking for a way to incorporate some outside of the box homework Gnowledge would work really well for your students. This would also be a great way for you to change up your method of assessment in class if you have computers available to you. You could even have this be a center in your room so that students could take the test in rotations while the other students were engaged in the classroom.