I have a funny smelling goo coming from my belly button. What is this?

Depends. It could be something as simple as lint or dirt from daily activity. If the goo persists it could be a persistent urachus. The urachus is a embryological remnant of communication of the bladder to the umbilical cord. If this doesn't close, then urine can leak out this opening. See a physician to determine if this is the case and it can be surgically corrected.