From Music Hack Day
LazyDJ is an app for lazy DJs who do not want to think about what song they should play next. It's designed to work well on mobile (Android, iPhone, iPad etc) so it can be used surreptitiously whilst DJing at a party. For now it lives at http://lazydj.mixcloud.com/ You search by song name for the song you're playing and it will use the Mixcloud API (http://api.mixcloud.com/) to look up mixes containing that song and suggest songs that popular mixes have played next. You can keep clicking through to build yourself a playlist based on Mixcloud users' expertise.
 The technology