Check out Top Ten SaaS Buzzwords from James Maguire

Here are a few more:

SaaS-enabler: a company/technology that can take an enterprise/offline business and replicate the functionality in terms of SaaS services. Essentially convert a non-SaaS application into SaaS offering.

SaaS vs. ASP: ASP (Application Service Provider) is a client-service architecture deployed over HTML. A “pure” ASP does not support a multi-tenant model. Each instance of the application/service may be customized for clients. ASPs may also take a licensed product and host it (as well as operate, maintain, support) for clients.

SaaS vs SOA: SOA (Service-oriented architecture) is a software architecture that supports loosely coupled software services that impart some business functionality. These services can communicate but it is not required. SOA may be interpreted as the underlying platform for SaaS. More on Wikipedia.