I've stopped using the term "Cloud Computing" except when referring to the general trend. I use SaaS, IaaS and PaaS so that I say exactly what I mean. As a technical person this helps me keep my conversation succinct and focused.

SaaS: Software as a Service: Salesforce.com, Google Apps, etc.

PaaS: Platform as a Service: Google App Engine and similar systems.

IaaS: Infrastructure as a Service: Amazon EC2, Eucalyptus, etc.

SaaS: It's a web site!

PaaS: It's a framework!

IaaS: It's a VM!

Or, if you want a way to remember it easier:

"Cloud" is what marketing and non-technical people use. I'm ok with that.

And one more thing. I've found this article is good for giving to managers and other people that need to understand the terminology and get up to speed on what's happening: Communications of the ACM: A View of Cloud Computing