This is a fantastic website that I saw in action during Susan Muir's lesson today!  There are too many activities to describe in detail, but it is basically a free, online resource base for developing numeracy and literacy skills (and more) at multiple grade levels.  It is really just something you have to check out for yourself.

TES iboard

I was chatting with Darla today after school and happened to notice a website that she had stumbled across called Mathwire.  The site has a ton of alphabetized links to different Math activities and also sites categorized according to NCTM standards.  What really caught my attention, though, was the "Math Music" page.  It lists a bunch of songs already categorized according to strand that you can listen to online for free!  I'll link to the Mathwire home page and I'll also link directly to the music page as it takes a bit of digging.

http://mathwire.com/
http://mathwire.com/music/music.html