xnots is a desktop post-it / sticky note system for the unix geek. All post-it notes are text files in some directory. Changes made to files in this directory automatically propogate to the displayed note. And yes, notes can be transparent ... :)
Nice app, simple --- I have problems with moving notes and always-on-top in Gnome 3. Is this still developed (I hope it is)?
Simple. Useful. Light.
Useful and smart: it leaves the users decide instead of accept.