Time Tracking
I finally found a time-tracker that does what I want it to do. And it's online and it's free (open source). WR Time Tracker doesn't look very snazzy, but it's pretty fast and gets the job done. Adding activities is easy, but adding them to multiple projects at once is also very easy and that is something I have missed in other time-tracking software.

WR is tracking me as I write this post on my blog. So you can punch in and out or manually enter start and end times or a duration. You can also edit entries later if you made a mistake or decide you are going to bill your clients an extra hour here or there
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WR has an invoice generator, but to be honest, I am never going to use something like that as I like to make my invoices by hand with variations in the details included in them. So I'll stick to the ability to send time-reports to myself as e-mail. (You can also export to CSV or XML, but I can't be bothered to find a way to then have those values displayed correctly - Excel makes a mess of the CSV).