Can work on almost any webcomic/manga page, preloads 5 or more pages ahead (or behind), navigates via ajax for instant-page-change, lets you use the keyboard, remembers your progress, and it's relatively easy to add new sites

To help with reading through the Macropod Madness webcomic archive ( http://www.bibp.com/macropodia ). Will automatically load and append the next comic to the bottom of the page, so you can go through the archives by continually scrolling down, rather than continually clicking "next." Each comic page also links to its url archive position.