You can only use the official Microsoft USB wireless dongle.
The alternative is to use a wireless bridge device which connects to your 360 via cable and is then wireless from there to your router.
Examples from OcUK (though there are more devices available from manufacturers than listed):
http://www.overclockers.co.uk/productlist.php?groupid=46&catid=1002&subid=254
causes lots of lag too
causes lots of lag too