I've thought before about giving forum badges (or maybe even forum BTC credit) for donating x BTC to Bitcoin-accepting charities,
No theymos don't involves badges, I see a situation where forum users will only donate just to be recognized via badges which goes against the whole idea of charity. I'll love it, if every one could donate anonymously e.g I won't what to be judge based on the amount of bitcoin I can afford to donate.
And about the selection of charity organization, to avoid sending funds to fake charity we should only accept registered charitys and if possible only those that accepts bitcoin, this will encourage more charity into accepting bitcoin so they can tap into the blessing coming from Bitcointalk.org as a result we are also contributing to the adoption of bitcoin. Also the charity selection should be distributed across all countries and continents.