Radio.blog.club -
"Save your favorite tracks and build-up your playlist. Then listen to your juke.blog player." Great way to find new music - just search for a track and see what other music it leads to on other radio blog members' playlists.

Radio.blog -
"Radio.blog is the first stand-alone player that lets you stream sound on your website." Just download the zipped files and follow the instructions to create a nifty player to stream your tracks on your blog or site. (Important: your server must support PHP for this to work)