Elbert Caddick
Elbert Caddick voted up HappyTwo BeHereTwo's answer

Not knowing the type of trade show you're interested in, here's a site where you can search for shows with keywords.

http://www.expodatabase.com

This one has a calendar listing you may find beneficial.

http://www.eventseye.com

TSNN is another site dedicated to trade shows.

http://www.tsnn.com