cheekysod

I use TaskTrack:

http://www.bushsoftware.com/TaskTrack/TaskTrack.html

no setup required, and it tracks exactly how long you spend on each document during the day; so all you have to do is group the documents into tasks and you have the total time spent.

its actually made this stuff a heap easier than it was for me, I never used to bother until the end of the week, now I still dont, but the numbers are right :)