The first real, not-so-much-beta release of RFA Manager, an open source RFA editing program for Mac OS X by yours truly is out. Get it over at http://code.google.com/p/bmmt/.
It's fully localized in german and english, and it can do what you'd expect it to: Remove files, add files, create new folders, extract files, the deal. It can also save and open the game in a single step, which may be a neat little shortcut. You can also search for file names and file contents, and you can edit text files without changing the application. And of course it has all that you'd expect it to have, such as unlimited undo/redo, drag and drop, the usual.
So, if you have a Mac with Leopard, go check it out. If not, go buy one and then check it out. Official forum is over at http://bfmods.com/, where Cartoonfield also resides.
Update! Version 0.1.1 solves the problem of not being able to open certain (most) compressed files. So if you have 0.1.0 and find it's useless, go get 0.1.1.
Update again! Version 0.1.2 solves even more problems, such as not being able to edit files, not opening windows or dialog boxes not going away. It also adds automatic updates. Sorry for all the many releases, I promise I'll calm down now.