Seed swapping wasn't something I thought about until some months ago; giving away extra seeds, well yes, but swapping saved seeds in an organized fashion is definitely (major) fun, as well as being an important part of perpetuating vegetable varieties.
I came across this website about a seed-saving event in Toronto; hmm, if snowy climate places encourage seed swaps, why not us warmer climate folks?
There was a nice seed sharing booth at the Carolina Farm Stewardship's annual meeting last fall. We were invited to take samples of seeds (in small manila envelopes) to try -- what a great thing to offer up. I haven't saved seeds myself yet -- but it's an excellent thing to save open-pollinated varieties, many of which are 'pass-a-long' or heirloom varieties.
It's traditional (and vital) in most of the world to do so.