What is a United States crisp 1977 100 dollar bill serial number J 06643750 A worth?

$100 because it's not rare or very old Auction prices as of 03/2009 are slightly above face value for a crisp circulated specimen. Uncirculated it could bring up to $120. Note that a bill's serial number is just a counter and generally doesn't help to identify it or affect its value. There are collectors who will pay a premium for bills with low or patterned serial numbers; e.g. 12345678 or 00000005.