Felt like doing a little research for you (yep, I am that bored sitting here in the FBO crew lounge!). Below is the link to the FAA's website that will allow you to search aircraft in several ways to determine the aircraft category and a plethora of other information about said aircraft. The easiest way I found to determine category is to do and N-number search and then scroll down to the category listed for that N-number. Hope this helps.


http://registry.faa.gov/aircraftinquiry/