#recsplease - the Blip.fm Recommender bot
Jason has put together a mashup (ah, that term seems so old and dated now) that combines twitter, blip.fm, and the Echo Nest. When you Blip a song, just add the tag #recsplease to the twitter blip and you'll get a reply with some artists that you might like to listen to.
This is similar to recomme developed by Adam Lindsay but recomme has been down for a few weeks, so clearly there was a twitter-music-recommendation gap that needed to be filled.
Check out Jason's Blip.fm/twitter recommender bot.