I stare. I don't care if they are married; all I'm doing is looking!
However, I will not flirt with or hit on a married man, even if he is giving me all types of attention. It is sad to report how many married and/or taken men have tried to hit on me. When I was younger and more naive, I automatically assumed a married (or even taken!) guy automatically had no interest in other women. Of course, I was quite wrong.
I go to the bodybuilder gym, so there are plenty of VERY HOT, very built guys. I will pretend to watch my form in the mirrors while I am really eyeing the gym the entire time.
I have also found that losing weight has made me twice the perv.