Can I use an Android OS card on the new Nook Tablet?
With the Nook Color it is possible to both root the tablet and install a custom ROM.  Some users have even gone so far as to setup their Nook Color to dual boot.  In this scenario, the unit will boot the stock Nook OS when allowed to boot from internal memory, or boot a custom ROM when instructed to boot from the SD card.  This is likely the scenario you read about with regard to an "Android OS card".

The Nook Tablet is quite similar to the Nook Color, but has been modified from the earlier device to have a locked bootloader that will only load a ROM signed by Barnes &amp; Noble.  While it is still possible to gain root permission on this device, it is not (yet) possible to load a customer ROM.  Due to this, you may not boot the unit to an alternative ROM stored on the SD card.  You can, however, install the Amazon AppStore, Google Market, GMail, and other apps to get more utility from this tablet.  You can find instructions and details over at XDA-Developers:

http://forum.xda-developers.com/showthread.php?t=1354487