Dr. John Marshall has a site entitled Sexual Physics. His motto is "Love is a matter of chemistry. Sex is a matter of physics."
In a Q & A format, Dr. Marshall seeks to answer questions such as "Sex at the speed of light," "It wasn't me... it was the rest of the Universe," and "Relativistic penile length enhancement." Particularly good is the short essay "Top 10 reasons why sex at the speed of light is not an advisable form of procreation" (which brings to mind the classic "Man of Steel, Woman of Kleenex," a piece about the problems of Superman having sex).
This is kind of the advice column for people who read XKCD and understand why it's so funny.