Stowell,
Just the Keyword file not yet into structured keywords.
You can use the 'Export' button from the Keywords dialog to save them. Then on the other machine, use the Import button to load them in. If you need to merge them, you'll have to do that manually with a text editor, meaning:
Export on both systems to a file. Merge the two files into a single file (you don't have to alphabetically sort them or remove duplicates). Then Import the merged file on both systems.
-Kirk