Hairmixer is a riot! You can upload a picture of yourself and then try on the hairstyles of all kinds of celebrities. I don't know about its educational value, but it is fun. It does remind of an old Apple program Goo that I used to run in my lab.
Colorblender is a great tool for creating a matching palette of colors to use on a website (or anything for that mater!). For someone like myself who can't match anything it is fast, easy, and easy to convert to different applications. It also has an image converter that lets you convert different kinds of files like gif to jpeg, jpg, or bmp.
Swivel is listed under visual arts, but it is actually a site that makes graphs and charts out of interesting data. You can also import your own data. This site would be a great site for real world data for math teachers.
For personalized music on the web I like both Pandora and Lastfm. Both create music stations around your choice of your favorite artist. I had both going at once and would turn the sound down on whichever one was playing the song I liked the least. It turns out on my 2nd try that Pandora requires a free registration but Lastfm does not. Also if you do not like a song on Lastfm you can hit stop and then play to get a new song.