This is kind of an odd one but something I stumbled across a few days ago. It's an iPhone app (Don't know if it works on Android) where you play a slot machine with free spins. You get points based on the outcome of the spin. Your points can be used for anything from credit toward certain apps to gift cards. For instance, I've been playing for a few days and have enough points to pay for some apps.
Spins: You get two free spins every day. You also get spins for downloading free apps and letting them sit open on your phone for 30 seconds. You can then do whatever you want with the app (e.g., delete it). Referring new users also gets you five spins the first time they download an app.
I play because it doesn't cost anything and there are actually a few apps I want that are prizes. A gift card is farther away, but possible. iPads are prizes at the very high end and look like they could take forever to earn.
My referral link is http://freeappslots.com?refcode=33quzkbo and you may actually need to hit the link on your phone. Feel free to start a Conga in the comments section.