Partyhero - Pass your friends the aux!
RetailMenot - The RetailMeNot mobile app allows you to find deals on the go for both online shopping and in store shopping.
Heartbeat - Listen to music with your friends together, on Spotify
Slickdeals.net - Slickdeals: The Best Deals, Coupons & Discounts on everything
TuneMeet - Chat with people who are listening to the same song
Honey - Honey is a browser extension that automatically finds and applies coupon codes at checkout with a single click.