CyanogenMod announced support for the Barnes & Noble NOOK HD and NOOK HD+ tablets earlier in the week. The catch was, while the support was announced the downloads were not yet available. That being said, those who happen to be sporting either tablet will be happy to learn those nightly builds are now ready to download.
Just as a recap, the builds available for the NOOK HD and HD+ are CM10.1 nightlies. Or in other words, while ready to be downloaded and installed -- there may be some issues. With that in mind, the files are available from the Get.cm website with the NOOK HD listed as "hummingbird" and the NOOK HD+ listed as "ovation."
Those grabbing the CyanogenMod ROM will likely also want to grab the Gapps file which will install the Google goodies. This is the one that will give you access to the Play Store. As many will be familiar with, CM10.1 is based on Android 4.2. Those looking to step even closer to the edge can also consider CM10.2 which is based on Android 4.3.
A ROM has come available for the NOOK HD+ (by way of the xda-developers forums), though this one is clearly listed as being an "experimental initial release." That all being said, the NOOK HD and NOOK HD+ may not be a top of the line tablet at this point in time, but a combination of low price and features from CyanogenMod and this could be an option to consider.
At present the NOOK HD is down to $129 (8GB) and $149 (16GB) and the NOOK HD+ is down to $149 for the 16GB model and $179 for the 32GB model.