Marijuana sold on Indian reservations somehow seems like a natural fit. Indian reservations are supposed to have the status of sovereign nations, so they can do a lot of things that Americans are prohibited from doing. They've scored big with casinos, and the sale of tax free cigarettes has been a long time profit maker.
Now some tribes are contemplating the sale of marijuana. See Indian Country looks to marijuana as new moneymaker about a tribal pow-wow at the Tulalip Resort Casino in the state of Washington.
Several states have already legalized recreational marijuana, Washington included, but the tribes could easily compete on price if they don't have to collect the state tax.
The real payoff would be the extent that the new competition hurts the drug cartels.
As for new businesses for tribes, I've long thought they would do well to establish webmail services and toss National Security Letters in the trash. Now there's a selling point.