Simple week-calendar based time tracker and invoicer
saus.us
saus.us
Another part I like is how Saus, while aimed at tracking time for multiple projects that you do for multiple clients, it is still very easy to use for single projects (like in my case).
Since we only use the time tracking part I have not given the invoicing a try.
Disclaimer: Saus was created by friends of mine, so my opinion could be biased. Though I wonder if it is more biased that opinions based on marketing and trends :). Either way, give it a try if you want, or not, I just wanted to share ;).