john,
Ok here is a way to move the "categories" over, per say. It will only work if both the macs have the same fonts, or at least those fonts only on the new machine you move the "categories" to will work.
Ok here is what you can try. The folder you need to copy from one mac to the other is ~/Library/FontCollections ( ~ = Your Home Folder). Just Copy the whole FontCollections folder from Mac A to Mac B and put it in the same location. Keep in mind do this while Font Book is closed or else you will have to restart Font Book.
Hope that helps,
Weston