Cat A
C172/ 182/ 210, Piper Warrior/ Lance/ Saratogoa/ Cherokee 6
Cat B
Aerostar, B58, King Air 200/350, 400 series Cessnas, Piper Navajo/ Chieftain
Cat C
I think, but not sure, all 737s and 767-200.
Cat D
B767-300/400, B747-400
Not sure about any of the Airbus types. I'm sure someone will tell me I'm wrong but I hope this helps.
As a very rough guide for what you're looking for most piston singles will fall in Category A, turbine singles/ piston twins/ light turboprops - Category B, heavy turboprops and light jets up to 737 sort of size - Cat C and heavy jets ie. anything else - Cat D.