browsershots.com is OK, but it's much easier, in my opinion, to view the site in other browsers natively. All major browsers are free downloads:
Mozilla Firefox Google Chrome Apple Safari (for Windows) Opera
And, as frustrating as it might be, you will probably want to test in Internet Explorer's current and past versions, as they have highly different rendering capabilities. I've found an incredibly useful tool, called IE Tester, that allows you to view all versions of IE using one program. Here's a link:
IE Tester Download. Note: it's Windows only.