There are other programs...There's Johnson, Engineer, and Sandbox...those are the ones I know of, besides Forge. But Forge, in my opinion, is still the best, because you don't need the .map file to mod in Forge. I think you need it in Johnson. I don't really have any experience with Engineer or Sandbox, but IMO, forge is the best.
It has Xport, Xplorer, Johnson, Forge,Sandbox,Engineer, and lot's of other utilites needed ot mod Halo 3. It has multiple resigners(Use CON), and a Hash Calculator, which I don't know what that is for but...hell, you might need it sometime.