another one i'll second is definitely pathfinder. BAD ASS app. i could damn near get by just using that with no dock at all. unfreakingbelievable. and they have a new version coming out very soon, so if you buy, you get a free upgrade

another kinda cool little app is quicksilver...you just <ctrl><space> and it pulls up a little window, and you start typing...it pulls a list of programs, or files, etc. and you select the one you're after.
you can also set up hotkey triggers for various programs' functions (i.e. volume up/down/play/pause/stop, etc for itunes), and it has plugins for various programs (omniweb, mail, etc). it's amazing how easy it is to get used to/spoiled with.
i think someone had posted a pref file that you could replace the dock pref file with also...i think it moved the dock to a corner and shrunk it, too.
i'd kinda like to know if there's command line stuff to prevent the dock from ever showing on screen at all, but to at least give me the hotkeys for hide/show, etc...
yahoo's doing konfabulator these days for free, also...and you can assign it to use f-12 and effectively use it in place of the apple widgets.
that's just scraping the tip of the iceburg for osx tweakages!
fun stuff.
kell