Is there a way to sync custom shortcuts (general and application specific i.e. Xcode) between two macs?
Dropbox syncs folders & files between two machines, and creates a backup on the cloud. Symlinks enable you to create links to other folders & files on your machine that need to be stored/placed somewhere other than your Dropbox folder. Sort of like desktop shortcuts on windows. Using the two together will enable you to keep any media you wish in sync between two machines, not just your Dropbox folder.
After installing Dropbox, open a terminal
ln -s /Users/yourUsername/folderIWantToSync /Users/yourUsername/Dropbox/folderIWantToSyncTo
the folderIWantToSync is probably going to be the keyboard shortcuts preferences file. Not sure where that is, but if you do this on both machines, the file will stay in sync between the two machines, thus your keyboard shortcuts (I believe this is the type of shortcut to which you are referring) will be the same on both machines.
The link below shows you how to set up dropbox with symlinks. http://iboughtamac.com/2010/05/05/symlinks-dropbox-awesome/