[Shohan]

Another vote for Mobipocket's mobile and desktop clients. Able to read, convert multiple formats, and sync them to your PPC. Remembers your last page, click a button to advance or touch the sides of the screen to turn the page (requires checkbox option in settings). It also has the option to auto scroll, with configurable speed, so you don't have to press a button or touch the screen.

Audiobooks are great too, but I don't find them practical on my Mogul. The battery life with the lack of bookmarking, as mentioned, is a downer. Much prefer my iPod for audiobooks myself.