I a chart addict . I am using mynfp.de, nfp-forum.de and fertilityfirend.com
I don't like FF that much because they have too many default and you need to put it right yourself because they have a funny method of calculating a chart. also if you want the full version it is ridiculously expenisve lol. my nfp cost 11 euro a year, nfp-forum.de (kurvenreich) doesn't cost anything it is free and there are others which are also free at charting too.