Hiya. In my own work today for an agency, I came across the December 2011 Search Consultant List, published by the 4As. To get it, follow this link. True smarties will note the differences between this list and past ones.
Again, these are search consultants. Some of which on this list serve both client and agencies. Be forewarned. But should you be a relatively large agency, you should know a bit about search consultants. Potentially good distribution for you.
A broad overview of this segment of our business is here. You can also find more here. This last link is a link to the blog posts that mention “search consultant.” Lots of information here. Some of it even helpful!