ISBN # for an eBook?

No. You'll need to either buy a block of them from RR Bowker (http://www.isbn.org ,) the sole U.S. supplier, or publish the ebook through an established publisher. If you elect to buy a block, then YOU'LL be listed as the publisher at Amazon, BN.com and others, and will probably need to create a business entity to handle whatever tax filing requirements your state has. If you use a company, that's handled as part of the overall fee.

Have you signed up as an ebook seller with Amazon yet? If not:

http://tinyurl.com/y7u67t

and find out if you need an ISBN (the same with the other vendors or wholesalers you plan to deal with). Technically, I think you would need an ISBN for every format you release:

"If an online publication is available under different operating systems and/or command languages, each «edition» would require a separate ISBN." -- http://www.isbn-international.org/

In the real world I don't think this happens, which suggests that ebook firms insisting on an ISBN are doing so for their own internal purposes, and not for the purposes for which ISBNs were designed.

Boy, am I glad I wandered over here today! The site owner I've been working with is still pushing the e-book idea, but I honestly never thought about the ISBN number issue. He's not a publisher, so he certainly doesn't own any, and I'm not likely to buy an entire block just for one e-book.

I'll be following this thread with great interest.

How is he planning to market the ebook? If it's just from his own website, then there's no more need for an ISBN than if he ordered a stack of paper copies from a local printer and offered them in the same way.

If the ebook is to be offered through other retail channels, then the ebook will need to comply with whatever those channels' ISBN requirements are.