Yes, you're right SOAP is but one way that services can be exposed. A lot of people are using RESTful style services to build their service platform. In the Java world, you may find it sufficient to use just plain old XML (POX) over JMS. SOA certainly doesn't equal SOAP, though that seemed to be the focus years ago when the term first emerged.
In my book, I describe how Apache Tuscany, an SCA implementation, can be used as a framework for building components and exposing them as reusable services that multiple different bindings, such as SOAP, REST, RSS etc. (Obvoiusly, there are other outstanding SCA frameworks such as Fabric3).