Recently, I’ve discovered that the most recent update for the Nook Color and Nook Tablet has given the Nook built-in support for CBZ files. CBZ is a popular digital comic book format online—mostly found with smaller press or independent publications, public domain materials, and (yes, I know) pirated materials. CBZ is merely a renamed ZIP file containing sequentially numbered JPGs. A common companion format of CBZ is CBR (a renamed RAR file).
Testing some CBZ files on my Nook Color shows it displays the comics just fine. While there’s no support for CBR files, converting CBRs to CBZs is fairly straightforward (in Xubuntu, right-click on the CBR and select “Extract Here,” then right-click on the extracted files’ folder and select “Create Archive,” then select “CBZ” from the drop-down menu and click “OK”).
On a related note, I wonder why Barnes and Noble doesn’t offer the Comixology app. Despite the heavily DRMed nature of Comixology’s comics (proprietary files only readable or accessible within the app; basically a glorified rental model), it seems to have become the most popular online legal comics venue. I suppose it’d mean less sales of B&N’s own digital graphic novels, though.