I have used sub-domains in

I have used sub-domains in various ways – I have my main domain (www.birdcat.com) but have done work for others and hosted it for them in a sub-domain, then all they needed to do was get a domain name (only about $10/year) and redirect to my sub-domain (for example, my http://www.7squared.com just redirects to video.birdcat.com). This way, I find it easier (and more cost effective) to manage just one (or few) true web hosts but can have many different sites.