Letterflix - Send letters and snail mail online to the USA, Europe, India, or anywhere in the world. Letterflix is the easiest and secure way to send letters and snail mail anywhere in the world from the comfort of your home.

Quip - Quip is the modern productivity suite that simplifies your life and helps your team get work done faster.

Letter to Yourself - Send a physical letter to your future self

Google Docs - Create a new document and edit with others at the same time -- from your computer, phone or tablet. Get stuff done with or without an internet connection. Use Docs to edit Word files. Free from Google.

SendLetters - Send Documents, Invoices, Letters physically to anywhere in the worldHave Documents Printed, Folded and Mailed by us, starting at $1

Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.