I don't have any tests to prove this, but switching from a 64-bit kernel to a 32-bit one and forcing apps to run in 32-bit mode helps a lot with memory usage on OS X.
You can use this app to switch apps to 32-bit: http://www.macupdate.com/app/mac/40405/sixtyfour
If you look at Windows 7 memory consumption with the same set of software you use in OS X, you'll notice memory usage is 1/2 or 1/3 on Windows compared to OS X. Maybe someone knows why that is?
If you look at Windows 7 memory consumption with the same set of software you use in OS X, you'll notice memory usage is 1/2 or 1/3 on Windows compared to OS X. Maybe someone knows why that is?