Neuter Neuter Land
I found this website, it's got some great thoughts and ideas for promoting Spay/Neuter, it's run by the "Neuteress of the Night". I especially love some of the slogans, examples:
"If you walked around naked all day, all you'd think about is sex too. Spay and neuter your pets today!"
"Any cat will tell you,
"Neuter your dog!!"
Any dog will tell you,
"Neuter the darn cat!"