Got to agree with MadDog on this one. Unless you are going to jack
around with something like MS Project, then the watch and some database
of notes is the way to go for me.
When I'm working on a web site, I rarely work on just 1 or 2 pages. I
have a set of goals that I try to accomplish. If I'm on an hourly deal
(or just trying to gauge my time), then I make a note of when I start,
what I do, and when I finish. Then I record that information in my
client's files or wherever.
There are probably better ways to do this with software, but I haven't
found anything yet that actually "saves" me time. Most of them actually
cost me more time trying to work with the app to track the time.