Question: We have some boxes at a reputable (expensive) hosting company.

They don't offer a simple/flexible VM solution.

All I want is the ability to create CentOS VMs (mainly) to host our (mostly) static sites (corporate etc), maintaining the big boxes for more traffic/DB intensive services.

Any suggestions.

Answer: 
I'm a fan of linode - <http://www.linode.com/>
I don't think you can get cheaper prices than <http://www.prgmr.com> 

They have very good, personal support as well. They've been very helpful with performance issues I had from ordering too small of a machine initially. 

My blog is hosted there, and I'm happy with it.