IETester is a free WebBrowser that allows you to have the rendering and javascript engines of IE8 RC1, IE7 IE 6 and IE5.5 on Vista and XP, as well as the installed IE in the same process.
New in v0.3 : IE8 RC1, zoom feature and a lot of corrections and improvements !

This is an alpha release, so feel free to post comments/bugs on the IETester forum or contact me directly.
Minimum requirement : Windows Vista or Windows XP with IE7 (Windows XP/IE6 config has some problems and IE8 instance do not work under XP without SP2)