Interesting question about the ISBN. In the US, they're issued/registered by the Library of Congress. Anyone interested should probably be able to get current information from the LOC.gov website, or you may see the application form at Bowker.
RRBowker is the publisher of Books in Print and is the only approved agent for issue of US ISBNs by email/internet. Minimum fee appears to be about $75(US).
A few years ago, the LOC was complaining that they'd run out of numbers for new publishers. They were threatening to use this as a reason for refusing to issue ISBN to "small" publishers.
The base number is 9 digits, the first five of which are supposedly unique for each publisher. The next 4 digits would identify a specific book from that publisher, and the "dash" digit - a number or "X" - usually indicates an edition. The last dash usually differs for paperback and hardbound versions.
An ISBN is useful only if your publication is going to be handled by "resellers." It provides a way for them to look up how to contact the original publisher if someone wants the book. The "cheap out" is to print your name, address, and phone number in each book, and sell them yourself. Mel Bay does it that way.
If you are outside the US (and not registering a US copyright) you have to go to your own country's agencies.
It's been a number of years since I've looked at this, so be sure to get the latest from the appropriate sources before sending money.