ISAPI Rewrite
You really need to check out ISAPI Rewrite. I've used it for so long that I forgot that many people haven't even heard about it.
ORCS Web hosts this web site and www.DozingDogs.com, some secured staging web sites and under development sites (about 10 in all) all on a single, cheap, shared hosting account using ISAPI Rewrite.
This is huge, and quickly quiets people who whine that hosting is expensive. 10+ web sites running independently on a shared account? Do the math.
(In case you'd like the elevator description of how it works, it uses regular expressions to seamlessly transfer requests to a sub-folder containing the correct web site - it's 100% supported by our CMS)
The reason I'm bringing this up now though, is because one of my customers just asked me, "Is ISAPI Rewrite Lite ok?"
I'd never heard of a Lite version so I head on over to their site to read about it. It looks like their Lite package would work just fine for many people and is totally FREE. That's a good price right there, hard to beat..