I was playing around with customizing my Dock tonight and even though I had made a copy of the Resources folder, somehow the files didn't get copied correctly, so I ended up loosing most of the contents of the folder. 
I wasn't able to just activate the Time Machine interface and restore Dock.app since it was "in use" (because, it was, I don't think you can kill it right? otherwise this would have worked ), but I was able to navigate the Backups.backupdb directory and nab an earlier version of Dock.app's Resource folder files. (note I first tried to get a copy of the Dock from the Leopard install DVD but even after toying around in Terminal looking for files I wasn't able to find any installer packages with it in it!)
I wasn't able to just activate the Time Machine interface and restore Dock.app since it was "in use" (because, it was, I don't think you can kill it right? otherwise this would have worked ), but I was able to navigate the Backups.backupdb directory and nab an earlier version of Dock.app's Resource folder files. (note I first tried to get a copy of the Dock from the Leopard install DVD but even after toying around in Terminal looking for files I wasn't able to find any installer packages with it in it!)