Amazon now offer a POD service via their sister company Createspace. You write your masterpiece, convert it into pdf format and upload it to their site. You have to be very careful to stay within the parameters that they require or they bug you with emails explaining that your file isn't 'quite' right... yeah I had a few *cough*
Then you have to design a cover (which I gave up on as my graphics looked like a five year old's) and so I trawled the web for something suitable. I found what I wanted on deviantART , an abstract design of a comet (the story is about what happens when Earth encounters a possible KT-Extinction Event - like the one around the time of the dinosaurs) the artist is Jan Mullins an Australian lady who kindly did not ask for payment (who, however, will want a share of proceeds if the book is turned into a film by Spielberg)
At the moment the only drawback I see with the system is that it is only Amazon.com who do all the printing and stocking of titles, awkward for UK customers, but from what I can understand they will be extending into affiliate countries in the future.
So, if you like end of the world scenarios, comets, mad killer robots, Navajo Indians then this might be for you!
You can always read the first two chapters here and see what you think.