Colorado and Washington kicked down the door of pot prohibition in 2013, and several more will try in 2014, but only three are really considered by pundits as having a good chance.
Alaska comes first; it looks like voters in the state will have the chance to decide on legalization this summer, and they have the Marijuana Policy Project backing the pro-legalization side, fresh off their victory with Amendment 64 in Colorado.
Oregon is another good possibility, with three separate measures looking to get on the ballot this fall. Measure 80, which would have legalized certain amounts of recreational marijuana possession, failed in November 2012 while advocates in WA and CO were riding to victory. A similar bill died in the legislature in 2013; advocates hope that trying to put the measure before the voters in the November 2014 may push the legislature to get the job done before then; in any case, polls indicate that voters are looking for a good measure to support.
Rhode Island is another good possibility for 2014, and they may end of being the first state to legalize through the legislature. Like Oregon and Alaska, RI is a medical marijuana state and they also recently decriminalized some possession. Also like AK and OR, a majority of Rhode Island residents have shown in polls that they support recreational legalization. A bill backed by MPP failed there last year, but had some good support behind it; advocates think that just a little more is needed to make legalization happen in the smallest state in the U.S.
California is going to make a run at legalization yet again, but in-fighting between advocates and advocates (and advocates and growers) may once again foil legalization in what should have been the first state to get it done. The battles are preventing the necessary money from flowing into the CA legalization effort, handicapping the possibility and probably pushing it to 2016.