Something I've been looking for: Finder Window Manager

Check out this post from The Unofficial Apple Weblog (TUAW):

This simple utility allows you "to save and restore your window placement and view options via Window Sets." You can have different Window Sets for different purposes (e.g. different projects, etc.). Just arrange the Finder windows as you'd like them and take a snapshot by creating a Window Set; later you can easily restore these settings through the menubar item (right). There are also a bunch of window management options in the Utilities submenu, such as stacking and tiling, etc.

(from: Finder Window Manager)