MIUI, a popular third-party ROM for Android devices, is now available as a stable version for the B&N Nook Color. It's worth noting that this is not part of the official MIUI project, but a faithful port from the folks at MIUI.us -- like many of the English language releases. It's built from the latest 1.7.8 release (July 6), which has a page full of bugfixes and optimizations, so you're getting the very latest version for your eReader turned awesome Android tablet.
As of right now, there looks to be an issue mounting the internal storage (the developers have acknowledged and will fix in the next release) and you'll need to download something like softkeys or button savior to have access to the standard Android buttons. The next release will bundle button savior to save you that step. Other than that, the feedback looks very positive. You can find the download links and more information at the source link below.
Source: MIUI.us. Thanks, Thoth19!