Lulu is an American publish-it-yourself company. DH used it to publish a book he wrote. They don't charge you anything for publishing per se, but they take a percentage of the profits--basically, they say 'OK, it'll cost us $12 per copy, you can charge whatever you want', and you can charge $20 or $50 or whatever you please, as long as they get their $12. They print the books off one at a time, so you don't have to get rid of a whole 'run'.
The catch is you have to send them your book as a PDF, and however it looks on the PDF is EXACTLY how it will end up--they don't go through and fix your margins or spelling errors or change the typescript if it's too small, or anything. DH designed his own cover for his book, but if you're not artistically inclined you might need to get someone else to do it. Anyway, DH is very impressed with Lulu, particularly because he gets to keep all intellectual property rights, which enables him to put his book online for free. 'Real' publishers won't let you do that!