A hub or router would do exactly what you want. You'd have to spend a little however.

http://www.practicallynetworked.com/sharing/dsl.htm

That site has info on setting up a shared DSL connection. You are more than likely going to have to buy some software and set it up yourself. Or switch OSes. Or as I said above invest in some hardware.

http://www.pppindia.com/intl/pppshar/pppshar.htm

Something like above should help you share your internet connection. But I am not sure though as I don't use Win2k3 Webserver edition.