The Forum Directory entry for Hacks adds- "Sidecars & other cooleo 2+ wheeled moto-contraptions
." Its easy to consider trailers towed by motorcycles as just one type of cool contraption used in the motorcycle environment.
If you seek websites detailing trailer builds, try the following link which includes three more at the page end:
Home Made Motorcycle Cargo Trailer
I tow something similar in the form of an Easy Trailer 830TA
; a 48" x 40" tiny car trailer, which was modified for lighter duty work behind a 650cc Suzuki.