Tick, a time-keeping service currently in closed beta, was created to keep its developers from going over budget on their own projects. Unlike other time-keeping tools that are primarily focused around billing for time (see 1time), Tick is designed to help its users keep track of the time they've budgeted for projects so that they don't go over budget and cut into their profits.
Tick is one of those superelegant new Web 2.0 sites. It's simple and easy to use, and it appears to have just enough features to be useful. Users can set up multiple projects, clients, and workers, and quickly tell who has worked on what and which projects are running over their allotted time.
One thing Tick can't do is make your time budgets accurate, unfortunately. For that you might want to look at Devshop, a project management service with a unique "risk-based" scheduling philosophy.
A time-recording desktop widget is also in the works.
The service will be free if you are managing only one project, which can have multiple tasks. Paid plans, ranging up to $79 per month, will let you track multiple projects and employees.