JA Konrath has offered to give $500 to the charity First Book if his novel Trapped reaches the top 100. Better yet, if it reaches the top 20, he'll donate another $500. That's a total $1000 to a great charity just for supporting a great book and a talented author.
Mr. Konrath did this before with another novel and First Book benefited with a $500 donation. Read all the details at his blog Newbies Guide to Publishing.