Here's a nice application for people who work by the hour ... and must track those hours themselves. Timepost works very simply - just click the start button as you begin working and the pause button when you're done.
Now for the good part. Timepost integrates with Basecamp, Freshbooks, Blinksale, FogBugz, Harvest and Tick. Just enable the API access for each service in your account settings and you'll be able to browse all of your open projects. Select the one you're working on from the drop down menu and when you're finished just click the "Post" button. Your hours will be added to the project.
Timepost requires Mac OS X 10.4.9 or later and a single license will cost you $49US.