I just found this really nice service called Browsershots.org. You just type in an URI some distributed computers (mostly Linux) visits the site and creates the screenshots. The images appears after a few minutes.
It is perfect now in the changing times between IE6 and IE7 since it's not possible to have them installed on the same computer. It can be done with the unofficial stand alone versions, but I heard it doesn't work that good.
Browsershots.org currently supports the following browsers:
I tested beta 3 a bit and it looks very good. It's a bit irritating that you can't (as far as I know) run both of the versions on the same machine. Since I have a big need to test websites on IE6 I was forced to uninstall IE7.
Now we are waiting for the final realease (due this autumn). The big question is how well it will suppport the web standards from World Wide Web Consortium. Hopefully it will be much better than the old IE6 which lacks in a number of areas.