On The Core Knowledge Blog, Robert Pondiscio cited a newspaper column bemoaning the disappearance of the Little Golden Books and other inexpensive children's fare; that columnist noted that the books are available in some places, mostly online. While I don't agree with the premise—I have seen The Poky Little Puppy, etc., in Walmart, for one—the blog did get me to thinking about affordable books for little ones.
The public library, of course, is the biggest bargain; library cards are free.
Here is a version of what I wrote in the comments at Core Knowledge:
Goodwill and other thrift stores are excellent places to buy inexpensive books for children, as are library sales. Tag sales and garage sales are other good places to look, not to mention online resources like Freecycle lists and Paperback Swap. Almost all libraries offer free Internet access, so one does not have to own a computer to have accounts or join email lists.
My local Goodwill sells children’s paperbacks for something like 50 cents. The various Scholastic clubs also offer at least some inexpensive books in almost every catalogue. (A tip: just avoid the books that come with the cheap tchotchkes. Breakage=heartbreak.)
Any other ideas? I hope you'll add them in the comments. I'd be happy to make the suggestions into a flyer.