I was cruising around the internet today looking for an answer and i ran across the Slicehost guides. I remember a while back using those for my first Debian Lenny setup. I checked to see what kind of resources they had for CentOS, since I pretty much only work with Red Hat these days.
For someone just starting out this series of articles lay out the basics of getting setup like no other site out there.
Here is the link to the whole page of articles related to CentOS setup on a slice: CentOS Setup Guides
If you are looking for a good place to get your feet wet, then I would recommend Rackspace, On-Demand Linux and Windows Servers on the Cloud. I can create a virtual machine, use it for a few hours for testing, and pay less than a dollar.