In this Episode of The Complete Picture (Merging Individual Lightroom Catalogs into a “Master” Catalog) I will demonstrate how to combine individual Lightroom catalogs into a single, “Master” Lightroom catalog to simplify a photographers workflow and enable multi-shoot searching.

The BIG problem with doing this is that you loose your connect with your Publishing Services. I tried this and found that I would have to republish all my photos to SmugMug.
Hi Julieanne,
What about going the other way… taking a Master catalog and splitting it into multiple smaller catalogs to speed things up when handling catalogs?
Thank-you,
Ethan Garrity
That is covered in the second half of this tutorial – enjoy!
http://tv.adobe.com/watch/adobe-evangelists-julieanne-kost/episode-12/