Miniature Mail - Little letters printed on demand and sent in tiny envelopes.
Handwrytten - Handwritten notes straight from your device. Huge selection of cards or design your own. Handwriting service integrates with 1000's of apps.
MailThis - Send mail from your computer
Handwriting.io - Real handwriting without the pen – no robots, all software
The Simple Postcard - Text a photo to mail it as a postcard
Future Me - Send an email to your future self