Grooveshark is a music site similar to iTunes. Build your own playlists, mark favorites, and add songs to your personal library.
Last.fm is a music social networking website. Create your own radio station and use the charts feature to track your most-played songs. Post your charts to Facebook and MySpace to share your changing music tastes.
Bands use MySpace to promote their music. Use MySpace Music to create playlists of up to 100 songs which can be shared.
Use Pandora to create radio stations based on your favorite music artists. Pandora has an excellent recommendation feature that you can tweak to get you listening to new music you'll enjoy.
Playlist allows you to create streaming playlists that can be posted to your blog, website, or favorite social network. Add a total of 200 songs to each playlist you create. There is no limit to the number of playlists you can create.
Use YouTube to create playlists of your favorite songs and music videos. Comment on songs, share your playlists with other users, and check out the top 100 most popular music videos on YouTube.