Xen is a open source software that permits you to create server type of virtual private server. Using Xen you could build Linux, Windows Server, FreeBSD, Solaris virtual machines.
There are many companies which give you the change to buy a xen virtual private server like linode, vpsmedia, vpslink, slicehost.
Linode cheaper vps stars 19.95 $
Linode 360 MB RAM $19.95 12GB HD 200GB bandwith
Slicehost starting plan costs 20 dollars:
256 MB RAM $20 10GB HD 100GB bandwith
VPSMedia sells entry virtual server to $20:
384 MB RAM 15 GB HD 150 GB bandwith $20
Xen link-3 plan on Vpslink has these features and costs $19.95:
256 MB RAM 10 GB HD 300 GB bandwith $19.95
These web providers offer some cheap vps solution. If you have less than 20 $, you can buy a 384 MB of RAM xen vps.