http://www.khanacademy.org/ - is a great resource for students to learn just about any math subject.  Sal Kahn created this system starting with a pen tablet, a screen recorder and a PC.  Mr. Kahn works his way through each concept by working the virtual problems will narrating and providing strategies for solving the problems.  Very simple and very effective.

Students can make use of our extensive video library, practice exercises, and assessments from any computer with access to the web.  Coaches, parents, and teachers have visibility into what their students are learning and doing on the Khan Academy via a built in tracking system.

This is a non-profit organization and all of the content is free.  Really, really great stuff.  Take a look at it for any level of math that your students (or yourself!) may need.