I've been pretty happy with toggl.
Ask HN: What do you use for time tracking
11–14 of 14 posts
Re: Ask HN: What do you use for time tracking
#12freshbooks.com - time tracking and invoicing in one package.
I use Freshbooks as well, so far it's been well worth $20 / month, but if you don't have many clients/projects you can use it for free.
Re: Ask HN: What do you use for time tracking
#13I'm using Yast, cool startup from Norway. I picked this one because it works on desktop and Iphone, possible to add subprojects with different pricing model, share data with another team-members/freelancers, comprehensive reports and has very good API. URL: http://www.yast.com/
Re: Ask HN: What do you use for time tracking
#14http://www.tickspot.com/ is also pretty good. Paid version sync to Basecamp.