.annoy was a program written and created for unix by the Masters Of Deception (MOD) from New York. Mac.Annoy is a similiar program ported for Macintosh. The program dials a victims number over and over again until you tell it to stop.
Very, very annoying. Hence the name. Read the 'How it works' dialog in the apple menu for more info.
Future versions may include harassing audio messages, logs, and who knows what else...