"Online cloud based HTML5 filled Markdown Editor. Sync with Dropbox, Github and Google Drive. 100% Open Source!"
"Full-featured, open-source Markdown editor based on PageDown"
"task tracker and outliner for tech‑savvy teams and individuals. If you aren't into code and text editors this will make you cry"
Exchange passwords with others
https://github.com/unicalabs/agrippa (PHP w/ Laravel)
"free online whiteboard that lets you draw online with a group of friends all at the same time or by yourself"
"a fast markdown processor for writing professional articles, books, manuals, webpages and presentations, with a focus on simplicity and plain text readability."
"Peer-to-peer file transfers in your web browser."
ASCII art text generator with support for a huge number of fonts
highlight, copy, and translate text from any image