Giftcard Zen - Buy a gift card at a discount
Charity Navigator - Charity assessment application.
Wirize - Payment checkout for freelancers
GivePulse - GivePulse is an online community for volunteers, manage event registrations, event listings, marketing, and more.
Google Payment API - Enable an easy-to-use checkout experience for customers
ACH payments with Stripe - Accept bank payments with a few lines of code.