Maryland's electors for president are voting this morning, making today, in a sense, the acutal election day. But in this state at least, there's no suspense whatsoever. In some states, "faithless electors" can go out on their own and vote for whomever they like today, but that's not the case in Maryland. Section 8-505 of the elections article of the Maryland code specifies that "the presidential electors shall cast their votes for the candidates for President and Vice President who received a plurality of the votes cast in the State of Maryland." So here, at least, they are theoretically bound to follow the results of the election here, which went handily for Barack Obama.
What would happen if an elector broke that law? The code doesn't address that. Some states have specific penalties for faithless electors, and some nullify their votes. The last case of a faithless elector came in 2000 when one of Washington D.C.'s electors chose not to cast her vote for Al Gore (as she had pledged to do) as an act of protest for the lack of Congressional voting rights for the district.
Of course this could theoretically all change. Maryland was the first state to pass a law that could circumvent the electoral college altogether. It says that the state will award its electoral votes to the winner of the national popular vote (not the state's popular vote). But it only goes into effect if states with a sufficient number of electoral votes to constitute a national majority pass the same law. That way, the winner of the national popular vote would always win the electoral college. (Assuming there aren't any of those pesky faithless electors...)