A MOAT client interacts with a server to:
Clients should check that the meaning URI is the URI of a resource, not an HTML page
Screenshot:

Will be included in SparqlPress
OpenLink DataSpaces (ODS) features a MOAT client that can be used when tagging content. Actually, as soon as some content have been tagged using MOAT in an OSD instance, the ODS instance also becomes a MOAT server.
A complete documentation about MOAT and ODS is available here.
LODr is an application that apply the MOAT principles (and so interacts with a server) to existing Web 2.0 content from major services (Flickr, del.icio.us ...). A complete overview of LODr can be found on its dedicated website.