Tracking time spent and billable hours doesn't have to be difficult, even if you work for multiple clients and not all of your working time is spent in front of a computer. Toggl (free; $5/month plan offers more features)) is a Web-based time tracking system with a downloadable client for Windows, Mac OS X and Linux as well as mobile applications for Android and iOS.

If you're working with multiple clients and projects, you can also specify a client and a project. You can also tag the task, which is useful for tracking the same type of task across multiple clients and projects (like tracking all design-related tasks, versus coding-related tasks). And if you've already started working on a task some time ago but forgot to start tracking it, you can edit the start time even while the timer is counting, and the duration will update on the fly. You can also add tasks without using the timer, by simply noting their start and end times.

In terms of functionality, the desktop client looks like a simple iPhone app, and works well. You can track new tasks, create new projects and clients, and edit past tasks, but when the time comes to generate reports you'll still need the Toggl website.

Toggl's free version offers a generous subset of features. The paid version adds support for teams larger than five people, tracking billable vs. non-billable hours, different billing rates for different projects, Quickbooks and Basecamp integration, and more.

I found the free version of Toggl more than enough for my needs, but at $5 per user per month, the paid version is very affordable too.

Note: The Downloads button takes you to the vendor's site, where you can download the latest version of the software.

--Erez Zukerman