Cryptpad is for working collaboratively on documents such as Rich Text, Spread Sheets, Presentations, Whiteboards, and Project Boards.
The server has no access to any of your data and the encryption is based on zero knowledge. You don't even need to give an email address to register - you pick a username and a password and that is used to create encryption keys used by your browser to decrypt the files stored on the server. Neat.
I'm going to start using this more than Google Docs or similar as it is quicker, does not track (or request logins of collaborators), and it's hosted in France.
Try it out.