I snapped this tip up on Apple's mailing list: projectbuilder-users@lists.apple.com. Full credits to the author, Mike Ferris.
You can modify any keyboard shortcut in any Cocoa app using the very powerful defaults system. The key you want to modify in your defaults database is NSUserKeyEquivalents.
The following example would set the Activity Viewer menu item of Mail.app to be command+shift+A:
defaults write com.apple.Mail NSUserKeyEquivalents '{"Activity Viewer"="@$A";}'The odd characters before the 'A' in the previous command, specify the modifiers:Mac OS X Hints
http://hints.macworld.com/article.php?story=20010415090359962