I have found that YouTube has some awesome tools for homeschooling. My favorite is Khan Academy which teaches math through YouTube videos. Here is a sample video
The History Channel also has a presense on You Tube with 248 videos availble for your viewing leasure. Here is a sample.
There are also numerous foriegn language tutorials... this one is more fun than instructional:
For younger kids, you can also find the full library of School House Rock videos