Nebraska and Maine... I found this answer at the electoral college FAQ website
Maine and nebraska
Maine and Nebraska use a unique system for allocating their electoral votes, differing from the winner-takes-all approach used by most states. Both states employ a proportional method, where electoral votes are distributed based on the results of the popular vote within their congressional districts, as well as statewide. This allows for the possibility of splitting electoral votes between candidates, which can influence overall election outcomes more significantly than in states that allocate all votes to the statewide winner.
Nebraska and Maine do not simply award all their votes to the state-wide winner. They award one vote to the winner in each separate congressional district and two votes to the state-wide winner.
Those two States are not Winner Take All Statesand their Electoral Votes may be split between voting districts as was the case for Nebraska in the 2008 Presidential Election.
Most states appoint their electors on a winner-take-all basis, based on the statewide popular vote on Election Day. Maine and Nebraska are the only two current exceptions. Maine and Nebraska distribute their electoral votes proportionally, with two at-large electors representing the statewide winning presidential and vice-presidential candidates and one elector each representing the winners from each of their Congressional districts.
The District of Columbia and 48 U.S. states (all except Maine and Nebraska) utilize a winner-takes-all rule for the Electoral College. In a winner-take-all state, all of the state's Electoral votes go to whichever candidate receives a majority of the popular vote, or a plurality of the popular vote (less than 50 percent but more than any other candidate). Maine and Nebraska use the "congressional district method", selecting one elector within each congressional district by popular vote and awarding two electors by a statewide popular vote.
Maine and Nebraska allow for the splitting of their electoral votes. I think they both award one elector to the winner in each Congressional district and give the other two votes to the over-all state-wide winner.
Oregon does not split its Electoral College votes. Since the election of 1824, most states have appointed their electors on a winner-take-all basis, based on the statewide popular vote on Election Day. Maine and Nebraska are the only two current exceptions, as both states use the congressional district method. Maine and Nebraska use the "congressional district method", selecting one elector within each congressional district by popular vote and awarding two electors by a statewide popular vote.
Two states, Maine and Nebraska, use a tiered system where a single elector is chosen within each Congressional district and two electors are chosen by statewide popular vote.
None, but Maine and Nebraska each bases two electoral votes on the popular vote of the state and each additional electoral vote on the popular vote of each congressional district.
They can if their legislature votes to split their votes. Maine and Nebraska currently allow their vote to be split.