Why does it have to be so different depending on gender? I understand that in most (practically all) indigenous cultures had significant differences between the rites of passages for girls and boys, but for crafting rituals for adolescents coming of age in modern society, I think we can get creative, and they don't have to be too different. For girls it makes sense for the rite of passage into adulthood to be centered around their first moon time (menstrual cycle) - it is a transition dictated by our bodies, universal to female-bodied people around the world.
It also makes sense to me that women should be mentored in that transition by women elders, and boys mentored by male elders, although personally I think that it is essential that both also be guided, at some point in the process, by elders of the other gender as well. Also, in modern society the younger generations are rapidly moving away from gender distinctions altogether - making the binary gender classification obsolete - and I think that is a very very good thing, in the sense of everyone feeling free to determine their own identity and gender expression.
I also know that any society that I am a part of MUST respect each individual's free choice as to how they want to contribute to the community, and I will passionately fight any attempts to impose gender roles, like women doing the gathering and cooking, and men doing the hunting and fighting in battle. I understand that most traditional cultures did have roles like that, and I respect those cultures, but I myself must have free choice to choose my own path, and I will fight for that same right for all children around me (that are not members of a traditional culture with its own traditions). Does that make sense?
The fundamentals of any rite of passage are universal: some kind of physical/mental/emotional/spiritual trial or hardship, where the individual faces death, and the choice of either facing their fear and accepting that death (of the old), so that they can be reborn in some way, or resisting that death and failing the test - either to try again later, or physically dying (the danger was real, in many culture's traditions). Anyway, there are many sources who can explain this better. But the point I'm trying to make is that the essence of the rite of passage is the same no matter if you are a girl or boy, entering adulthood or becoming a shaman or warrior or whatever. They only differ in the particulars.
Personally I don't know any specific examples of rites of passage into adulthood. Does anyone else know of any, or can recommend good sources of info about this?