If you have a large domain, then you probably also have a large number of rooms and resources defined in your directory. This list can be so large that it makes it difficult for your users to find the entries for their particular site. Here is a simple way to make resources easier to work with.
This will require that you have directory assistance setup with a secondary directory that is used only by servers that will share the subset of rooms and resources. Create the rooms and resources as usual in the primary directory. Copy the appropriate room and resource documents for that site from the primary directory and paste them into the secondary directory used by that site's servers.
That's it. Now teach your users to switch to the secondary directory when selecting a room or resource to reserve. The only entries that will appear are those for the sites you copied into that directory.
Note: The entries in the secondary directory are only used for selecting the names of the rooms and resources. Domino still pulls all data associated with them from the primary directory and all reservations are still stored in the resource reservation database as usual. So if you change the name of a room or resource, you will need to re-copy the document from the primary directory to the secondary directory whenever you make a change to them. But this is a small price to pay in a domain with hundreds or thousands of rooms and resources.