Anytime you need immediate help with a specific math problem, you can probably find it on the Internet. No, these sites aren't going to look at your work to see where you went wrong, but they might give you that one step that you are missing in solving a problem. Below is a list of my favorite math help sites:
There are also a lot of great math blogs out there! Here a a few of them.
And this page wouldn't be complete without links to fun math activities!