This document provides an overview and comparison of several popular open source automation tools, including Selenium, Watir, FlexMonkey, TurnkeyLinux, TestLink, and Redmine. Selenium is a suite of tools for automating web browsers across different browsers and operating systems. Watir is a Ruby library for automating web browsers. FlexMonkey is a tool for testing Flex and Air applications. TurnkeyLinux provides over 45 ready-to-use Linux solutions. TestLink is an open source test management tool. Redmine is an open source project management and issue tracking tool. The document compares the pros and cons of each tool and provides example usages and links for further information.