Math sites

In perusing the Promethean Planet, I found a blog dedicated to teaching math.  It is called Mathematics Teacher's Lounge.  On the blog I found a number of links to other sites that would be helpful for teaching math. One is from  the public schools of North Carolina site.  It is a list of leveled pdf files that can challenge your students to use critical thinking and problem solving skills. It can be found at Math Stars Newsletter.  
Math 5 Alive is a site with explanatory videos and demonstrations, activity sheets, assessments, and parent and teacher notes on a myriad of math topics. Reminds me a bit of Brain Pop.
Scholastic has become a great resource for interactive lessons.  On Scholastic's Study Jams you can find an intro video, quiz, and vocab on fractions.  Take a look around, there are lots more great lessons.
Add Em Up is a fun demo game found on the Math is Fun site.
Be sure to check out the forums, blog, and teacher features on the Planet for lots of great ideas.