I also get asked this ALL THE TIME. :->
As of this moment, *Microsoft* has released a NAP Client in Windows Vista and will be releasing a Windows XP NAP Client in forthcoming XP Service Pack 3.
No other NAP Clients are planned by Microsoft at this time. Instead, we are working directly with partners so that they may provide NAP Client support to the "ecosystem". It should be the same experience as buying a 3rd party Anti-Virus or Firewall.
I have discussed the Avenda Systems Linux NAP Client we showed in N+I Vegas here on the blog. I hope to be making a Linux update as well as an exciting Mac announcement soon!
NAP the WORLD in 2007,
NAP Release Manager
* Remove the "online" to actually email me.
** This posting is provided "AS IS" with no warranties, and confers no rights.