mixmello - mixmello is a free, open source tool to create remixed versions of your favourite playlists.
Gnoosic - Even if you don't know what you are looking for - gnod will find it.
Incredibox - Express your musicality, pump it up and chill
BandNext - Discover bands that sound similar to artists you already love with BandNext. A single click saves your results to a Youtube playlist.
Musicroamer - A visual Pandora for discovering new music
Remix of the Century - A mix of every #1 from the Billboard charts since 1890