I recently set-up a OSX Snow Leopard Server running in Virtualbox.
What you need:
A computer running Virtualbox w/ at least 3 GB of RAM
An Internet Connection
An Apple OSX Snow Leopard Retail CD
*This is for testing only and not met for production.
First I installed OSX 10.6 following this article.
Once that was done I created an inexpensive server using this guide
enjoy : )
Posted by Josh