As a side note to Catch's excellent post, you can aways publish your work yourself at
Lulu.com. Here you can sell your books online, or for a small fee get an ISBN so that your book can be sold in your local bookstore. Or, for a (substantially) larger fee, Lulu will distrubute your work to some of the largest book wholesalers in the world, which can then be bought and sold by bookstores worldwide. What's even better is, your works remains your own property, and you keep 80% of your profits.
This is relevant to the topic, so this ain't shilling. I'm just sharing with you guys something cool I found.