02-23-2010 10:26 PM - edited 02-23-2010 10:27 PM
Legally? No place that I know of. Sony has some for its ereader, but they are not nook compatible.
The nook is not the best device for reading standard sized comics or graphic novels. The standard American comic book is 8x11, and the downsizing to fit on the nook makes it virtually impossible to read. Manga, being normally much smaller, fares better, although it can still be hard to read in places.