Lulu, is probably the cheapest way to get started with self publishing. You can publish one 6x9" black and white 50 page book for $5.53! You don't need to create a ISBN or bar code for you book, if you don't want to. Check out their price sheet.
From what I hear they also print your book very quickly.
Lulu was founded in 2002 by RedHat Linux co-founder Bob Young, and is quickly becoming one of the hottest self publishing outfits.