HSM stands for
High School Musical, which is a disney film that is highly popular among all girls 16 years of age and under.
But lets be honest - its the biggest crap ever. The main characters are
Vanessa Hudgens (err... a whore) and Zac Efron (a total fag). I've watched it once and the plot has obviously been pulled out of someone's arse.
There is a lot of HSM merchandise that can be found
practically in any store.