There are as many different lengths as you want there to be; if you want to cut it down to feet, there are a different number of lengths than if you cut it down to inches.
Personally I've always cut it down to:
Bouncer, Long-Hop, just-short-of-length, good-length, full, Half-Volley, Yorker, Full-Toss, Beamer.
Of course, these lengths change relative to the height of the batsman, the bounce in the pitch and the height of the bowler, because they all concern the height at which the ball will reach the batsman.