We’ve looked at many time tracking applications for web workers in the past. timeXchange is another entrant in this crowded field, with a rather distributed feel to it. Anyone can sign up to use the free service; once you’re signed up, you can define projects (including things like standard tasks to use, cost and billing rates) and invite other users via their email. If you get invited, you follow a link, register, and then can start submitting your time and expenses to the project.
Features include multiple levels of time approval and reporting, PDF-format reports for administrators and clients, and central storage of everyone’s time on the timeXchange servers. It looks like a good fit for distributed teams or freelancers who come together to work in ad-hoc project groups but still need centralized tracking and reporting.