Wow, these links and resources are nice to put together as a sticky (or added to the one in Computer Hardware with a shortcut here).
I run Ubuntu (which is also nice to test in, as the Gnome windowing system DOES affect Firefox re fonts etc) with VirtualBox running two copies of Windows XP: one with native IE6 and Safari4, the other with IE7 and Tredosoft Multiple IE's for quick IE6 testing (extensive testing is done in the native) and Safari 3. For Firefox 2 I use K-Meleon which still uses the FF2 version of Gecko. This was a hell of a lot easier than playing with profiles (seriously, that's just silly).
What's also good about having either Linux or a Mac for testing is for stupid stuff like how Mozilla decided to destroy all PNGs on those OS's (I don't notice a problem on FF3.5 on Windows) to "enhance" pngs. What a terrible idea... my own site looks like some retard built it (ok, some retard did build it, but the png thing is Mozilla's fault, honest).
I'd love to know some cheap way of testing real Safari-on-a-Mac... without shelling out for a Mac.
I've resorted to waiting an hour for Browsershots to show me what Zapfino looked like on a site. Terrible.