Social Source Commons

Manages time expenses, generates progress, billing and overtime reports. Can export data for further use and analysis.

Billable is an application for Mac OS X that helps you keep track of the billable services you perform for a client and then lets you create and manage invoices based on those services.

ClockingIT is a free to use hosted application, keeping track of all your tasks and the time you spend on them.

The Gnome Time Tracker is a to-do list/diary/journal tool that can track the amount of time spent on projects, and, among other things, generate reports and invoices based on that time. It's being used it to keep shopping lists, organize ideas, track bug reports, keep a diary of activities, do some blogging, provide weekly status reports to management, and even as a consultant billing system.

Hosted service that supports tracking time, logging expenses, and creating invoices

Web-based service that combines time tracking and task management. Useful for those that bill on an hourly or project basis.

Full-featured time-tracking application.

A complete sales management program that includes: invoicing, estimates or price quotes, inventory management, automated billing, mailing list management, and sales tracking. Invoices and bills can be printed on plain paper or emailed directly to customers.

Simple, web-based time tracking with powerful visual reporting tools and mobile access

Windows time tracking software.

TimeLive time tracking software is an integrated suite for time recording, time tracking, expense tracking, project management and time billing software

Simple, easy to use, open source, web-based time tracking system.