Holding a party with your closest buds? You can have them help you out pick the tunes with Festify. The Windows and Mac app lets you build a Spotify playlist on the app. And then you can invite friends to vote on tracks using their mobile devices. Those that get the most votes will be played next. You will, however, need a Spotify Premium account to make use of this app.
Source: Lifehacker | Download: Festify (Free)