I love books. I love bargains. I love www.paperbackswap.com.
Give a book, get a book it's that simple. I posted 10 books I don't care to give away (all in good condition) and received 2 free credits. Each book is worth a credit. People asked for my books and I mailed them out. I asked other people for their books and they mailed them to me.
The most money I've spent on postage is $3 and the least I've spent is $1.78. I can even pay for the postage online and print it from my computer to save a trip to the post office.