Freemind is an open source freeware tool (written in Java) that allows you to do some basic diagrams (as well as mind maps, called in Portuguese as "Mapas Ontológicos").
Diagrams supported include:
- Mind maps,
- Fishbone diagrams (used for causal analysis and brainstorming sessions)
- WBS diagrams, and more.
You can download it here (I use the portable edition, no install required on all machines if shared via a Google Drive or similar cloud storage that automatically propagates to all computers you own):
http://freemind-portable.en.softonic.com/download
PS. You might want to read and know a little bit more about (Tony Buzan's) mind maps here, here and here.
(@2016-06-20: Added the PT translation)
