Internet Explorer 8, Release Candidate 1 (the first beta actually being considered for release) was released today.
You can get it here: http://www.microsoft.com/windows/internet-explorer/beta/
This follow up to previous versions of IE that I'm sure everyone is familiar with adds private browsing (with no history recorded for private sessions) and improved security features.
It also allows you to simulate earlier versions for websites that insist on a specific version.
And while you are at it, if you have a spare machine just laying around, or if you are geeky enough to use a virtual machine (like me) download Windows 7 beta too.
It's like an improved, faster Vista. But make sure you have the minimum system requirements and that you have no problem with the computer just stopping when the Windows beta expires on Aug 1.