Meet people through the internet carnivorous plant mailing list, or through the carnivorous plant journals. Even old hands in the hobby, with whom you have little or no trading leverage, may be willing to sell you some things for a few dollars and postage. Enthusiasts tend to be very nice and sociable. If you read a cultivation article in a carnivorous plant journal and the author includes an address, by all means write him or her. That person will be happy to hear from you and you may develop a trading relationship.
Some trading options are now available online.
Look at the growlists posted on the many web ring sites , and the trading post on Rick Walker's CP Database Page.