Google Payment API - Enable an easy-to-use checkout experience for customers

Handwrytten - Handwritten notes straight from your device. Huge selection of cards or design your own. Handwriting service integrates with 1000's of apps.

Giftbit Payment API - Stripe for gift cards

Mailjoy - Delightfully easy direct mail marketing. A DIY direct mail tool created for marketing and growth teams. Design, mail & track personalized direct mail postcards and letters. Digital marketers use Mailjoy to send data-driven mail campaigns.

Stripe - Online payment processing for internet businesses. Stripe is a suite of payment APIs that powers commerce for online businesses of all sizes. Use Stripe’s payment platform to accept and process payments online for easy-to-use commerce solutions.

The Simple Postcard - Text a photo to mail it as a postcard