Unix directories in the finder
Most Mac users don't even realize that there is a Unix based underbelly on their Mac, so it's probably good that those directories are not readily available in the Finder. For those of us that rock the Terminal on a regular basis, it can sometimes be frustrating that the only way to utilize the Unix side is through command line only.
Luckily God invented key command shortcuts! Press cmd+shift+G with an open Finder window, open or save dialog box and you can navigate to any directory on your computer by typing it in starting with the root directory. This is great when you want to use TextMate for editing or viewing config files. You may run into some permission issues, but some careful manipulation of what group you belong to can fix that.