NOOK Tablet booting CyanogenMod 7 from an SD card
http://liliputing.com/2012/03/how-to-...
This video shows a NOOK Tablet dual-booting CyanogenMod 7 and the default B&N version of Android. CM7 runs from the SD card while the Barnes & Noble software runs from the internal storage.
You can find instructions for setting up the SD card at the link above.