editor for BSP content?

I''m wondering what all you people who are making BSP levels, dungeans, buildings, etc. are using to created them and compile? I''ve got two programs, Worldcraft and Tread3D and have been playing around with Halflife maps so far. I tried making a simple house with the skybox around it but the PR Q3 converter tool didn''t like it or anything else I tried. Do you have to set it up in a specific format? Tread3D asks which game you want to create content for, should I choose Q3 instead of Halflife or any of the others? If I do need to use the Q3 option I don''t have Quake 3...where do I get all the wad files and such that the editor needs? Thanks, Rendar