Which USB wifi is compatible with the 2.6 kernel?
 

I've looked at the HCL but many seem to require ndiswrapper.

Have a look at http://linux-wless.passys.nl/query_h...php?hostif=USB

Many ralink based cards will work out of he box on most Linux distributions or you can install the opensource drivers from serialmonkey. If you happen to be in UK, you can get the cards from Dabs or LinuxEmporium (the cards are branded as Edimax). If elsewhere your best bet is to search for stores that sell Edimax wireless cards. Some Atheros based cards also seem to work well using the madwifi drivers.