Colorado
Amendment 64 would legalize up to an ounce of marijuana, and would tax the substance up to 15%.
Amendment 64 is passing with 54% amount voting in favor and 46% opposed with 71% of precincts reporting.
Oregon
Cannabis Tax Act Initiative, Measure 80, would allow for the cultivation and legal sale of marijuana in state-sponsored stores. The sale of marijuana would also be taxed.
Oregon's Measure 80 is failing with 55% voting against and 46% amount in favor with 60% of ballots reporting.
Washington
Initiative 502 calls for a 25% tax rate on marijuana sales implemented when a grower sells to a processer, when a processor sells to a retailer, and finally when a retailer sells to a customer, according to CNN.
Washington's Initiative 502 is passing with 55% polls in favor and 45% of polls opposed with 51% of ballots reporting.
If any measure passes, it will directly contradict federal law, likely launching a federal challenge in the Supreme Court of the United States, according to CNN. As Reason Magazine's Jacob Sullum notes, it'd be difficult for the federal government to enforce federal laws against marijuana in states which have legalized its recreational use.
Update: Massachusetts has legalized medical marijuana with 63% in favor and 37% against, with 83% of polls reporting. Arkansas refuted its medical marijuana proposal, the first state in the South to hold such a referendum, with 52% against and 48% for with 73% of polls reporting.