Many people are using Apophysis to make Flame Fractals these days. It is also a free program. My personal favorite is UltraFractal but it is not a free program. You should wander through the gallery and check, as many of the artists state what program they use. If you see one you really like and it doesn't say, you can IM the artist and ask. Most will be happy to tell you.

Fractals will always amaze me!