We followed the example from the old wiki and it works great. One minor issue is every time we click on a link to our custom protocol handler firefox spawns an extra blank page or tab. Do you have any tips for disabling this behavior? My feeling is it is more firefox than shotgun. Strangely it used to happen all the time and now it only happens some of the time. Internally we have a few ideas, but thought people here may have encountered the same issue and perhaps solved it (firefox 3.0 on linux).