Not the 720 does have Arionet drivers in ROM, but they are the old version and if the firmware on the card doesn't match the driver version Cisco wont warrant it to work. Also the 340 mentioned above doesn't have encryption support. The 342 does, as does the 350. There is a 341, but it's only 40-bit.
D-Link DCF-660 works a treat - it is a compact flash card and will need a compact flash to PCMCIA adapter - I manage to get 11 MB connection speed via my wireless router.