[If you don't know what NaMaBloMo is, please read here.]
So when and how did the month of May become National Masturbation Month?
Well it all started when Good Vibrations, a sex-shop in San Francisco, California (link here) decided to declare May the National Masturbation Month back in 1995. If we feel that the taboo around masturbation is yet to be broken in 2011, imagine what it must have been like in 1995? (Incidentally, 1995 must also be the year when I started consciously touching myself.)
Good Vibrations thought it was high time to raise awareness about masturbation and sexual health. The idea for National Masturbation Month was itself triggered after Jocelyn Elders (who was, by the way, the first Afro-American to be appointed Surgeon General of the United States, and that was in 1993; do the math) was invited to talk about AIDS at a United Nations Conference. Elders said that "[Masturbation] is part of human sexuality and perhaps, it should be taught." Due to the controversy that followed Elder's statement, she was fired by the White House in December 1995. (Thank you, Mr. Bill Clinton.)
However, Good Vibrations still picked up on Elders' suggestion and in 1995, the first National Masturbation Month occurred in San Francisco (and some other parts of the USA).