Typically Fish Extender (FE) information gets started in the Cruise Meet thread for each specific cruise. One person will usually volunteer to keep a list of those participating and take responsibility for distributing the list at various times.
The specific items shared through the FE exchange vary greatly. Some folks purchase small gifts, like Disney themed pencils, while others like to make homemade items, like customized magnets, to share. Some people go all out with pricier things, but it is really just an individual decision as to how simple or elaborate you get.
Some will make door magnets, by either printing on magnetic paper or by laminating regular prints of custom artwork and then attach magnet strips on the back.
The Sept 22-25 Disney Dream cruise meet can be found by going to the "Disney Line" forum and then the "
Disney Cruise Meets". From there you can use the "Search this Thread" tool to look for "September 22-25, 2011 Disney Dream Cruise". Once on that forum you can use the same "Search this Thread" tool to look for posts about the FE for this cruise.
Hope that helps,