What is needed to go from single Ethernet to many?
If this is for a prototype - consider adding a USB ethernet adapter.

If you're building a product, I'd consider an onboard ethernet switch chip. Like this:

http://www.micrel.com/page.do?page=product-info/fastether_sw.jsp


(source: micrel.com)  

The ADM6996 may also be an option, if you can find it.