Matching Up Hotkeys for OS X and Linux GUIs?

I use a MacBook Pro for my main machine, but also have a Ubuntu desktop. I get irritated about switching between command-oriented hotkeys and ctrl-oriented hotkeys (cmd-a on OSX = ctrl-a on Linux/windows). I've looked over a lot of forums and have found that Gnome doesn't seem capable of changing hotkeys, while xfce and fluxbox can. The ideal solution would be a way to change system keys in X, or at the system level — that way I can keep compiz. Does anyone have any ideas or know a trick to change system hot keys?