[slilo]

http://orgmode.org/

[erik998]

+1 orgmode is the way to go. Everything is kept in a text file and you can have multiple text files. It's a bit of a learning curve but a quick tutorial and some practice can get you going.

http://orgmode.org/worg/org-tutorials/orgtutorial_dto.html

The tab effects are pretty cool. It's the best way to track your ideas, tasks, notes.

[marc_c]

+1 to orgmode. Plain text, with tools to export into different formats (HTML, PDF...)