Although the site looks to be based in Taiwan, the video lectures are in English, and I like this one because it uses a Calculus text that I already own. The link is specifically to an intro Calculus course, but more courses are available from the site.
Among other things, YouTube is a great source of how-to videos and mini-lectures. Although CPS teachers can't access these (yet) in the classroom, they can provide a source at home of _how_ to (or in some cases, how _not_ to) talk about a topic. Also good for brushing up on math topics, or learning new skills. For free.
Free online tutorials. I like this one, because (a) it is okay for self-paced instruction and (b) it provides a way to track progress.
700+ vids available on YouTube on a variety of topics. See the Khan Academy site for more on how these vids might be used.
Geogebra is a free application useful for exploring geometry and algebra concepts. The program is similar to the pricey Geometer's Sketchpad, except -- it's free.There is also an active international user community, including wiki, to help with ideas on how to incorporate the application into instruction. The app continues to grow -- it now has a spreadsheet component as well.
Lots of stuff here, including an "online learning system", videos (flash) on solving problems,an online math competition, and an online comment. "designed for high-performing math students."
Flash math tutorials from the Digital Learning Commons.
Free online math courses in Pre-Algebra, Algebra I, Algebra II, and Geometty, plus ACT and SAT test prep help. Also has a help forum. Most lessons look to link to YouTube videos.