I am just getting started with couponing. I'd be interested in this info as well. A bunch of moms here in my community are going to be getting together soon for a coupon swap. I know I get lots of coupons I won't use so hopefully they'll need them.
On the website www.thegrocerygame.com in the forums they have coupon trains. You join a train and you get an address of who to send to. You mark your coupons, so you know when you get them back. You add the ones you don't need, and take the ones you do. It worked out well for me for a while, but I got a little bogged down.
You can trade coupons on my site in the coupon swappers group. You can join a coupon train or swap with individual members. Here is my site http://www.SwapSavers.com/