Windows/Mac/Linux: Mangle is a handy tool for formatting your Manga and comic collections for easy reading on your Kindle. It includes page sorting, downsampling, and auto rotation for fuss-free reading.
The Kindle, especially the new 3rd generation model, has a sharp grayscale screen that is well suited for the simple and crisp graphics of Manga and similarly drawn comics. The problem is the majority of Manga and comic scans are in image packages where individual pages correspond to individual images in a series. When viewing images the Kindle is very picky about file formats and numbering. As a result it often starts the sequence of images-as-pages in the wrong spot. It also doesn't support image rotating or image sorting. The built-in image view simply wasn't designed with the reading of Manga scans in mind.
Mangle preemptively corrects all these issues by renaming the files, rotating large images, downsampling so the images look crisper on the Kindle's grayscale screen, and tweaking the metadata of the images so the Kindle sequences them correctly. Mangle is a free application available for Windows, Mac and Linux and supports conversion of image files with optimization for all three generations of Kindle ebook readers as well as the DX and DXG models. For a neat side-by-side comparison between paper and digital editions of Manga comics, check out the Flickr stream of Flickr user TevK.