Originally uploaded by sillydog
Seed swapping is fun and inexpensive. Daves Garden at http://www.davesgarden.com has a huge Plant and Seed Trading area.
7,000 gardeners are listing 34,000 plants and seeds that they offer, and that they want.
On the main web page click on "252 Forums", and on the left of the forums page click on "Plant and Seed Trading."
This is free and you don't even have to sign in to read the posts here. Since the gardeners often list what town and garden zone they live in you can keep postage costs down by finding gardeners near you, or maybe even a gardener in your town that you can hop on your bicycle to swap with.