http://usd.edu/trio/tut/excel/

A fairly clear self-guided/self-paced tutorial on using Excel. I'll keep this one for when I have some time to learn more about Excel than the basic skills already possess. It's still a lot of reading and static diagrams not really making complete use of the capabilities of computer-based education, but for a free tutorial it's quite adequate. I especially like the way the author introduces and teaches the use of equations but it would also be nice to have some way of knowing where you are in any one particular lesson. But then again, it is free...