Hours is a time tracking app that enables freelancers and consultants to track time by client or project. While it lacks built-in invoicing features, it provides an easy way to monitor work hours for accurate reporting.

Rachota is a portable and easy-to-use personal time tracking application for Windows, Linux, Solaris, and Mac, offering tools for tracking work on projects, generating reports, and increasing efficiency.

ActivityWatch is a free and open-source automated time tracker focused on privacy and extensibility. It supports cross-platform tracking, custom plugins, browser extensions, and provides detailed reports to help users analyze their time usage.

AND.CO is a time tracking app tailored for freelancers. It offers features such as contract creation and simplified reporting, streamlining time management and client invoicing for independent workers.

TimeSlotTracker is a Java-based time tracking tool, offering a flexible way to record and report on time allocation for different activities.

Toggl is a time-tracking platform offering desktop, web, and mobile clients, with features such as idle detection, reminders, Pomodoro timer, and daily time tracking. It is widely used for productivity and efficiency, and includes open-source desktop apps and command-line tools.