[radiojasper]

Toggl Track

https://track.toggl.com/timer

[phforms]

This. Been using it for more than 6 years for freelance work and never had any issues with it. Also never paid a penny since it has a generous free plan and I never had much use for any of the advanced features. It has a simple desktop app for tracking and I can quickly see my hours on the dashboard with statistics, summaries for specific time periods, filtering, etc.

[d4rkp4ttern]

This is the best I have found. Also great if you are consulting/freelancing and want to generate reports to attach to an invoice

[dukeofharen]

Yes, plus one for toggl. I used to track my time in a text file, but this became cluttered very quickly.