To log bits of information quickly I added this to my .bashrc:
log(){ date >> ~/log/$* ; cat >> ~/log/$* ; }
I try to keep it simple but I keep several files. There is one for general ideas which is called "projects", another one to log new words I've learnt called "voc.en" (English is a second language for me) and so on.
For example:
log projects <enter>
write something cool... <enter> <ctrl+c>
--------------------
cat log/projects
Mo 10. Sep 07:16:02 CEST 2012
write something cool...