Browsershots.org gives web developers screenshots of their sites across 3 operating systems (Linux, Windows, and MacOS) and a bunch of different browsers:
Don’t have MSIE 5.5 anymore — but your client does? Have no fear, this tool will show you what your site looks like on that browser. You can further limit your requests to pages with Flash, Javascript, and more.
The service will queue your request (among about 200 others) and you can specify a time period for your browser screenshots to process. The default is 30 minutes, after which the process in the queue is terminated and your screenshots are lost. Therefore, unless absolutely necessary, it’s advisable not to run a job using all the browsers listed — uncheck a few.