Use a Bookmarklet to add songs to your "Play Later" queue, add them yourself, or have your friends collaborate on your queue.
Then listen whenever you like.
Your friends can also listen along while you take control.
Uses Rdio API ...
SpotCast for Spotify
Introducing SpotCast by @jazzychad
"It's like Turntable.fm for Spotify!"
DJ your Spotify or listen to other users' stations!
As a weekend hack project, I have created a little app for Mac OS 10.6+ that ...
♫ Transforms your iTunes music library into an interactive Jukebox
♫ Allows friends to queue up songs using their iPhone or other mobile devices
♫ Shares the party music experience through Facebook and Twitter
★★★★★ - Jukebox Hero is the Ultimate Social Music Player for ...
Jukio [formerly Anthm] is an app that lets people control the music in the places they go. Connect your Rdio and Spotify accounts, host a party, and you and your friends can request and vote on millions of songs.