MacOS has an option called "Internet Sharing" or the like. If you turn that on it will act as a router and will run a DHCP-server to supply your SAM with an IP-address via Ethernet. You don´t even need a crossover cable or a hub, as all macs detect the partners twist (or lack thereof) and twist themselves accordingly. Configuring the SAM to use it is easy too, so - don´t try it - do it!
EDIT: Don´t confuse "Internet Sharing" and "Web Sharing". "Web Sharing" on a Mac means that you run your own Apache to serve your own website from your Mac, which in todays world usually doesn´t help you much. I think they will drop that "Web Sharing" feature soon, if they haven´t already in Lion. (Note to self: check this when at home)
