A must-have in your toolbox. FinkCommander makes it easy for any Mac OSX user to download and install Unix/Linux packages, all from within its helpful GUI!
Ooh, what an exciting shopping list... ;)
FinkCommander is working away in the background on my iBook right now, installing a package with all sorts of dependencies and fusses, none of which I have to worry about, because FinkCommander is doing it all. Hit "Install" and get on with your work.
It updates its package list every time you open it, and you can do that manually as well. It checks for updates. I think it even does laundry, as long as you put your dirty socks in your PATH.