The categories seem to be consolidating into:
a. Service enablement platforms (including any services implementation languages such as .NET, JAVA, CICS, etc, but also Application platforms such as Oracle ERP and SAP).
b. Registry Repository (System of authority for service catalog, assets, processes, roles and policies).
c. Intermediaries (mediation systems including integration hubs, ESBs, brokers, WS fabric, intermediaries, smart adaptors, portal software, XML accelerator appliances, SOAP firewalls, gateways, application routers, Web Service Management systems, WS Management agents, system management systems and others).
There are many categories, but they roughly fall into these buckets.
This was first published in October 2006