The fear of Friday the 13th is called paraskevidekatriaphobia, a word derived from the combination of the Greek words Paraskeví (meaning Friday), and dekatreís (meaning thirteen), attached to phobía (meaning fear).
The term triskaidekaphobia (with which many of us are familiar) is only regarding the fear of the number 13... But paraskevidekatriaphobia is the actual fear of "Friday the 13th", and no, I don't mean the movies.
In case you hadn't noticed... TODAY is Friday the 13th. I hope you have a good one.
This year (2009) we had three months, where Friday the 13th done fell on a Friday... and we will experience the same thing in 2012, where we'll have the trifecta of Friday the 13ths.