No, but if one of your computers has 2 internet ports available (one wired and one wireless), you can hook that up to your modem using a LAN cable and share the internet connection wirelessly with the other computer. Of course, both must be wireless capable. If one or both is not, you can buy cheap USB adapters at any computer store.
Instructions on how to do this:
Mac OS X 10.5: http://docs.info.apple.com/article.html?path=Mac/10.5/en/8156.html