Mastodawn

What's the best open source app or utility that no one else has heard of?

(Please note that your replies may be read out and discussed on an episode of Late Night)

@LateNightLinux Zim Wiki. It's a FOSS note-taking/personal wiki manager that is amazing and doesn't get enough love.

Zim is a notepad like desktop application that is inspired by the way people use wikis.