when you've read the latest book you've purchased, what do you do with them, leave them on a shelf to gather dust?

I Use http://www.bookcrossing.com/about joun up here http://www.bookcrossing.com/join pick your screen name register the book then leave it in a place for someone else to pick up, also books that have been read by someone else and just left for the next person to read.

if you go to the link http://www.bookcrossing.com/hunt put in your country, county, town and look what books have been left for a new reader