YouTube's a great source of music, including live shows and bootleg recordings that are hard to find anywhere else, and application developers are taking advantage of YouTube's relative openness to help users find and organize that music in new ways.
Last month, London-based start-up TubeRadio.fm launched a Web application that lets you search YouTube, organize the content into playlists, and share those playlists with friends via an e-mail link, Twitter post, or Facebook profile update. If you go through the free registration, you'll be able to save playlists as well. The concept is very similar to that of Muziic, but without any software to download and install--this is strictly a Web application, like Grooveshark.
TubeRadio has a few interesting wrinkles that make it worth checking out. If you select the "Discography" tab, then search on an artist's name, it will return a list of that artist's albums. Select any album, and it will cobble together a streaming playlist of songs from the album in in the proper order--not all of the songs will be the original studio versions, but might be lower-quality live or bootleg recordings. It all depends on what YouTube has available.
For each album, TubeRadio also provides links to buy the physical CD from Amazon, or MP3 downloads from 7digital.
When a song is playing, a window at the bottom of the screen contains tabs with information such as lyrics (this doesn't work all the time, but seems reliable for studio-based recordings), plus an artist biography, discography, and suggestions for other albums you might like (the last three features are provided by Last.fm, which is owned by CNET News publisher CBS Interactive).
All in all, it's a slick and convenient way to discover the great wealth of music available on YouTube, and it doesn't cost a dime.