I use a number of them mostly here I post Apophysis it is a great program which can be used by itself or with gimp also free or with Ultra Ftractal which is not free nor is Xeno Dream. There is Fractal Exlporer, Sterling Ware, Xaos , Chaos Pro, V Chira, fractalus, Flight From Fractal, Tierazon Dust Fractal Snowflake Fractal just tons 99.9% are free programs and I think most are listed As Kansas said I'd suggest Apophysis plus get some of the free ones to try all of them what we like may end up not being your favorite ..Good Luck Carolyn