Ah, thanks for putting me on the right track, I believe I found it: http://www.textsnippets.com/posts/show/268
. Although acually I wanted to use this to add a key shortcut to switch users, the information I found there is still applicable. For anyone else who wants to know, the configuration path of "/apps/metacity/global_keybindings/" is used to hold keybindings for metacity and the path "/apps/metacity/keybinding_commands/" is used to hold definitions of the commands you can bind. I belive only the ones matching the pattern command_N (bound using run_command_N) are supposed to be configurable though. Also, you may want to use gconf-editor as it gives you a useful description of what all the stuff in your GNOME configuartion does.
Anyway, this should work nicely for my purposes. I'm suprised no one knew about this right off the bat though, as I'd think wanting to use keyboard shortcuts to launch commands would be desirable for a lot of users. One thing though, if anyone knows of a way to do this that will work with any window manager, and not just metacity, that would be even better. I'm not using beryl now, as it has quite a few bugs I find annoying, but I'm sure at some point in the future I'll want to use it and I don't want to have to lose my keyboard shortcuts in the process.