QATestingTools.com

Sahi is a free, open source tool for automation of web application testing.
Sahi is very tester friendly and allows easy automation of even complex web 2.0 applications with lots of AJAX content. With an excellent recorder, smart object identification, simple scripting, automatic waits and inbuilt reports, Sahi gives the tester a powerful yet simple tool to accomplish testing across various browser and OS combinations.
Sahi works on Internet Explorer, Firefox, Chrome, Safari, Opera etc. on Windows, Mac and Linux. (Sahi works on any browser which supports a proxy and executes Javascript. This means it supports all browsers since IE6.)

XMLUnit is an open source project licensed under the BSD license. It provides a small library of interrelated classes that simplify each of the different ways to test XML pieces that have been outlined in the previous section. Special APIs are provided to simplify writing unit tests with J/NUnit, but the library itself is fully usable without any testing framework at all. There is a Java and a .NET version of XMLUnit. XMLUnit’s APIs will accept “pieces of XML” as input using several different forms. In most cases they can be provided as InputStreams, Readers, Strings, InputSources or readily parsed DOM Document instances. XMLUnit also provides a Transform class that can be used to apply an XSLT transformation to an existing input.

WatiN (pronounced as What-in), WatiN has grown into an easy to use, feature rich and stable framework. WatiN stands for Web Application Testing In .NET, and it's a framework that enables web application testing through Internet Explorer.
The way that WatiN works is very "easy", knowing that there's a lot of work behind a framework like this. WatiN lets you open Internet Explorer instances, and through interop, interact with the elements in a form.
With WatiN, you can get and set values from the elements in a form, and you can fire events of any of the elements in the document too. WatiN is developed in C# and aims to bring you an easy way to automate your tests with Internet Explorer and FireFox using .Net.