Adobe is offering a free preview of its BrowserLab service, which allows Web developers to quickly see what their site looks like on a number of browsers. The technology, previously code-named ‘Meer Meer,’ uses virtualization, can show how a site will look in Firefox, Internet Explorer, and Safari running on different operating systems. Running BrowserLab requires a Mac or PC with Adobe Flash 10. Designers can compare a site in two browsers side by side as well as use an "onion skin" mode that shows a site in multiple browsers overlaid one on top of the other.
More info: BrowserLab