JukeBox - Free

Turn your phone into a jukebox! Start a party and your guests can queue songs that they like, from your MP3 collection! Create a dynamic playlist at a party. No login or setup needed! This is a free version which has some advertising.

You only need this app, a WiFi connection, and some music on your device. Since the app only needs a WiFi connection, it can be used with mobile WiFi hotspots on road-trips and picnics too!

Host a party and let your guests browse through your music collection and enqueue songs that they like.

Example usage scenarios:

[+] Parties
[+] Restaurants/Cafes/Bars - If you are an owner and provide wifi access to your customers, you can use your device as a jukebox and let your customers select the music that they want.
[+] Road Trips - set up wifi hotspot on one of the devices and connect all other devices to that WiFi
[+] Easy way to share the music listening experience with room mates and Hostel mates.
[+] Personal use - with multiple android devices. Start Party on your phone, connect it to the speakers. Enqueue songs from your tablet / second phone.

Note: This app does not require an internet connection. It only needs a WiFi network to localize the party communicate within the network. As a result, people who are not connected to the same wifi are automatically blocked from the party!