My favorite autism charity is ME.
I have earned far less in my working years than someone with my intelligence and education should have done, and my old age is going to be pretty restricted in terms of adventures. My former university friends are buying vacation homes or traveling all over the world in their retirement. Me, my big adventure is a subscription to Netflix.
I do sometimes donate to the Red Cross when there is a disaster, to Doctors without Borders, International Rescue Committee, Habitat for Humanity, and the local food pantry system. I am unaware of any autism "charity" that I feel I should be supporting.
So I am keeping my money to take care of my own needs - that is my contribution to the autism "cause."
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A finger in every pie.