The Barnes and Noble Nook Tablet is the most recent device issued by the company and many people are quite happy with it. After only a few days on the retail sphere the good folks at XDA have issued a new way to root your device.
The new rooting method gives you full access to the Google Android Market which gives you hundreds of thousands of applications to choose from and install right on your tablet. The new method is quite complicated and is not meant for the light of heart.
One of the drawbacks is that when you turn the power off of the device you will have to root it again. This is because of the encrypted bootloader that makes the tablet not easy to stay rooted. Because of this it may be sometime before CyanogenMod or Ice Cream Sandwich is ported over. You can find a step by step tutorial available at Liliputing.
Update: The fine folks at XDA Forums say this rooting process is now permanent. Check out the huge thread about it HERE.