While the stock Barnes & Noble NOOKcolor ROM has had a custom kernel capable of overclocking the 800MHz processor for over a week now, only now has SD-card-run Nookie Froyo gotten in on the action. Quickie "Screamer" 0.1 for Froyo cranks the CPU up to 950MHz.
The kernel is easily installed, by simply replacing Nookie Froyo's uImage boot file (backup first!) with this file of the same name. In Windows, you can simply drag and drop it onto your Nook's mounted SD drive, and reboot. Voila: you now have a faster Nook.
The custom kernel is Divine_Madcat's port of the original "Quickie" for B&N's ROM (which was developed by Geniusdog254).
The development community just keeps racking them up for NOOKcolor owners! [XDA Developers]