Being able to dual boot an Android device is pretty freaking awesome. You can use the separate installations to hide your second life or you can use it for more socially acceptable practices, such as having one installation for work and one for play. So, what does that say about triple booting? Without knowing anything about triple booting at all, one can assume that it is at least 150% more awesome than dual booting...
For those Mobotniks out there who are rocking a Barnes and Noble Nook Color, triple booting can be a reality for you. The process is a little tough, but if you follow it out you can boot not just one, not two but three separate installations from the spunky little tablet.
To begin, you'll need a Nook Color. Then, you'll need an SD Card that is 4GB or larger. Lastly, you'll need to be familiar with the process of burning a NookieFroyo SDcard. If you are unfamiliar with how that works, you can find a detailed guide in the nookdevs.com wiki.
Now that we are all educated and up to date, it's time to make this triple boot work.
First, download the modified image file. It's about 3.7GB so it'll take a second to download. Then download the ICS Gapps for dual boot from the link provided and the Gingerbread Gapps for dual boot from the link provided.
Once that's done, take that image and run on over to the nookdev.com wiki linked above and create a bootable SD Card with the image you downloaded.
From there, it gets a little loopy. Insert your new bootable SD card into the Nook and turn it on. It will boot into CyanogenMod7 as that is the default boot. Let it load up and connect it to WiFi. Then shut it down and boot again holding volume up and down while booting to boot into CyanogenMod9. Let it connect to wifi then shut down again.
From here, boot while pressing N to get to the boot manager. Navigate around and install the Gapps files you downloaded earlier. If you have any problems, consult the source link for additional details.
You've done it! Your Nook Color can now triple boot into stock on your EMMC, CyanogenMod7 on your SD Card and CyanogenMod9 on your SD Card. If that isn't truly glorious, then I expect proof of what is truly glorious in the comments.
Until next time Mobotniks!
Source: XDA Developers