Toggl - Toggl is an online time tracking tool. It features 1-click time tracking and helps you see where your time goes. Free and paid versions are available.
Empoche - Utilities, Application Utilities, and Task Management
Hours - Boosting productivity through live, virtual co-working.
Klokki for Mac - Rule-based automatic time-tracking
Futuramo Time Tracker - Futuramo Time Tracker is a time tracking solutions designed for freelancers and teams.
Freelancer Stack - Curated directory of tools used by 10,000+ freelancers