An indispensable program:
Open all the wads you want, drag all the textures you think look good together into one wad, only load that wad in the editor. Export/import from sane image formats to create your own additions! Hide stupid messages in your trigger texture! In a solid, utterly bug-free (albeit windows only) GUI app.
It's the best tool. Does what it says on the tin and it does it well.
What ever happened to Mickey? I heard he disappeared because he went broke and had to start couch surfing but that was ten+ years ago. (the economy is way better now!)