Grooveshark - Listen to any song you want online. You can also put Grooveshark widgets in your blogs or wikis.
Pandora - Great internet radio site. You can customize your radio station and it will play music that fits your preferences.
NeoK12 - Great resource for science. Games, quizzes, and videos.
Spelling City - Amazing website for helping students with spelling and vocabulary
Tripline - Tell a story or create a timeline using maps
Go 2 Web 2.0 - THE source for cool Web 2.0 sites.