Funny, I was doing some work in iTerm2 today and I found this really nice reference for OS X:

http://ss64.com/osx/

"A-Z Index of the Apple OS X Command Line"

The new one for me today was "ditto," which I immediately googled to see if there was a linux equivalent (there is, and it seems to be 'cp -Rp --parents src/ dest/').

Edit: Compared to the OP link I like that it doesn't truncate words arbitrarily to wrap lines :)

Edit2: Lo and behold, a bash version: http://ss64.com/bash/ ...and a Windows version! http://ss64.com/nt/ I like to see that. Useful site, with more at http://ss64.com/ (no relation to me)