I did a search for 'switching to mac' in Google, and there are a number of resources that come up, of course.
The first one I read was from LifeHacker: Hack Attack: A guide for switching to a Mac. I found this one somewhat helpful. For example, it confirmed what the funky little backslash-single-quote-looking icon is (the option/alt button), that the command button is roughly a mirror of the Windows control key. It also mentions something two or three of my new co-workers were talking about when I was at the office today - closing apps. It also has a number of links to further reading about various topics.
I think they mentioned the need to go to the Apple logo and pick the force quit option. First of all, it turns out that Mac has a three-fingered salute too - instead of Ctrl-Alt-Delete, it is Ctrl-Alt-Esc. It doesn't give access to as many functions, but it does take you straight to the Force Quit menu, which lets you pick any app and kill it. The article also talks about using Cmd-W to close the active window (but it doesn't close the app, so if you close the last window for the app, the app will still be in memory) and Cmd-Q to close the active app entirely.
The next thing I think I'll read is actually an Apple support page with what appears to be a fairly extensive tour of Mac Basics.