Several vendors are now supplying SoftAP (Host AP mode) utilities with their wireless adapters, notably ASUS and GigaByte.
I've tested the ASUS WL-107G and the ASUS WL-138G SoftAp support and it works just fine.
The PCTEL SoftAP was discontinued a few months back, but it also worked ok.
There is a How To file on this topic here:
http://www.nat32.com/nat32e/htm/asus.htm
Chris.