http://browsershots.org/

One of the key considerations in building a website is making it usable across multiple browsers on multiple operating systems. This site lets you submit your site's URL ( e.g., http://www.computeroutlook.com/ - the final / is needed if you're submitting the main page), then select which browsers on what OSes you want to see it. Submit and you'll receive a link to check back later to see the screenshots (and download them in a ZIP file).

Screenshots are deleted after 10 days of not being viewed.