From Richard Winger at Ballot Access News:
The Marijuana Party, which seems to be a party organized only in Nebraska, is petitioning to get on the 2016 ballot. The party needs 5,395 valid signatures by August 1, 2016. If it completes the petition by February 1, 2016, it can have its own primary.
While Mr. Winger believes the party is only organized in Nebraska, there is a national Marijuana Party, that this party may be affiliated with. The U.S. Marijuana Party has fielded candidates in some states, including Vermont and Washington.