For a lot of Android users out there, the Nook Color was their first exposure to the platform, or at least their first exposure to the magic of root and custom ROMs. The tablet's unlocked bootloader (from the days before B&N caught wise and started protecting its loss-leader business model) made it easy to convert into a "full" Android device. The CyanogenMod family of ROMs was one of the first reliable alternatives to the base software, and despite the aging hardware, the latest update is now available for the Nook Color. CM 10.1 (Android Jelly Bean 4.2) is now ready in nightly form.
Definition: A "nightly" is a bleeding edge release that is built on a daily basis, usually at night after a full day's worth of new code has been committed.