I still write a lot of stuff about science, but now I post it to my blog, Mystery Rays from Outer Space.
An urban legend:appears mysteriously and spreads spontaneously in varying forms contains elements of humor or horror (the horror often "punishes" someone who flouts society's conventions). makes good storytelling. does NOT have to be false, although most are. ULs often have a basis in fact, but it's their life after-the-fact (particularly in reference to the second and third points) that gives them particular interest.
Some vaguely science-related urban legends I found interesting: