sidetrack is probably my favorite 'app'/driver/hack/os x customization, followed immediately by QS of course. Coming from a windows world, 'right click' is ingrained. so having to hit ctrl and click was a nuisance. tapping the trackpad is a beautiful solution for me. course anytime someon use's my computer, their feather touch on the trackpad drives them crazy with contextual menu pop-ups. ;)

alas, another AWESOME prefpane I just stumbled upon recently (sorry, can't remember where else I'd ref the src) is autopairs. (http://www.jwwalker.com/pages/autopairs.html) it's mostly useful for coding, but somewhat in normal typing as well. whenever you type a '(' or '[' or '"' it automatically prints the closing ')' ']' or '"' AFTER your cursor. it's a little odd at first, but after a couple times it's natural. in normal typing it's marginally useful, but in coding it's great for those who are forgetful about closing their brackets etc.