Watir!

Selenium is a suite of tools specifically for testing web applications. Selenium IDE is a Firefox add-on that records clicks, typing, and other actions to make a test, which you can play back in the browser. Selenium Remote Control (RC) runs your tests in multiple browsers and platforms. Tweak your tests in your preferred language.

Kantu allows you to visually automate your task, and makes web automation fun again. It lets you create solutions for web automation, web scraping or web testing in minutes. It's like the ultimate robot stand-in for all of your web browser automation needs! Whatever you used to do manually, Kantu can do automatically -- stuff like filling out forms, clicking on links, performing inquiries, you name it, Kantu has it. Multiple page forms? Not a problem for Kantu.

iMacros was designed to automate the most repetitious tasks on the web. If there’s an activity you have to do repeatedly, just record it in iMacros. The next time you need to do it, the entire macro will run at the click of a button! With iMacros, you can quickly and easily fill out web forms, remember passwords, create a webmail notifier, download information from other sites, scrape the Web (get data from multiple sites), and more. You can keep the macros on your computer for your own use, or share them with others by embedding them on your homepage, blog, company Intranet or any social bookmarking service. The uses are limited only by your imagination! »

Pincers - Web automation DSL on top of webdriver (and nokogiri)

WatiN - Web Application Testing In .Net

Make test automation more efficient and help developers and testers collaborate. This functional test automation software—formerly QuickTest Professional (QTP)—helps deliver quality software at the speed your business needs. Use a single GUI for automating all types of functional testing. This easy-to-use visual experience helps you create automated testing for both GUI functionality and the back-end service (application business logic) parts of an application.

Mobitaz is a mobile app test automation application that tests Android apps. This end-to-end testing framework works as a Windows server with option to connect to an Android device or emulator that runs the app to be tested. Test cases can be created and tested in user specifications. The reports can be generated in HTML or PDF formats.

PhearJS renders dynamic webpages using PhantomJS: fetch a page, render it and return a pretty JSON object. PhearJS is offered as a hosted API as well as an open source solution that you can host yourself.

Ubot Studio allows you to make ANY automation software you want without ANY programming experience.

TestComplete is an automated testing tool, with unmatched support for unit, functional, regression, distributed and HTTP performance testing at the project level. Designed for advanced and novice testers alike, TestComplete will help you achieve thorough Quality Assurance in development from the first line of code right through delivery and maintenance, with no surprises along the way. Ship superior applications, and ship them on time.

FunkLoad is a functional and load web tester, written in Python, whose main use cases are:

CloudQA is cloud based test automation platform which will significantly reduce time, cost and complexity of your testing process. CloudQA does not need any test infrastructure. One could get started within minutes to record and execute a test case. CloudQA is easy to use, modular, accessible anytime anywhere with good scale.

This is a tool which is used to create your own HTTP bots, or use others. It is portable, has minimal interface and most important - it's completely free; even it recently became an open-source project! Also, it is lightweight - about 1 .5MB, very customizable and extendable with plugins.

Screenster provides visual UI test automation for web applications. It is the only tool that validates the screens that users actually see.