I find services that allow self-publishing quite interesting. Take Lulu.com for instance. All you have to do is write a book, upload it to Lulu and then start selling copies that are printed on demand (not that writing a book is easy). A perfect example of this can be found with Getting Real by 37signals. If you haven't read the 37 signals blog (origin of Ruby on Rails) and you're into web design, check it out. www.37signals.com
On a side note, books published on the internet don't require ISBNs, Getting Real doesn't have one.