According to their blog, the book publisher and distributor Lulu.com is now a "certified aggregator" for Apple's iPad iBookstore (also available for the iPhone this summer, apparently). You can convert your own book to the ePub format, upload it to the iBookstore, and reap 80% of the revenue as people download it to their iPads, via the iBooks app. Lulu assigns your book an ISBN number (as required by Apple) and guarantees that your book will pass Apple's ePub validation process if you let them convert it for you. For a limited time, this service is free, though you have to have an account with Lulu. If you already have an ebook on Lulu's site, this does not happen automatically: you must "opt-in" to Lulu's Apple/iBookstore distribution channel.