So your church group decides to pay for a new well somewhere that needs it. You'll have to collect $20 from each person, then bundle it all up and make sure no one's welching. That's a considerable amount of work for a big group, not to mention a lot of awkward conversations - you can only hear "I left my wallet at home" so many times before you snap, earning a scornful look from the deacon and a thrashing from your grandma after Sunday pot roast.
Tilt (formerly CrowdTilt) hopes to alleviate that problem, and by association, reduce the number of octogenarians with strained slappin' hands. It's a tool that lets organizers collect money for causes from every member in the group, using such whiz-bang modern methods as debit and credit cards (the latter have a 3% fee). While Tilt is primarily intended for smaller groups saving up for a common goal, non-profit organizations can use it to raise money directly or sell goods for a 2.5% service fee.
The real genius of the model is that everyone using the app (or the web version) can see who's paid, who hasn't paid, and how far off the goal your group is. That puts some considerable pressure on those who have yet to pony up, without forcing the organizers to go around and individually shame people. The interface for the system is surprisingly efficient as well - it has a lot in common with a Kickstarter page without the ridiculous overselling.
The Android version of Tilt is free, and works with phones or tablets running Ice Cream Sandwich or higher.