I've worked out what the results for the last six elections would've been, using the good old D'Hondt system for the popular-vote EVs. In each of these cases I've assumed that any faithless electors vote the way they were supposed to.
2012
Barack Obama (Democrat) – 51.1% – 608 EVs (332 + 276)
Mitt Romney (Republican) – 47.2% – 462 EVs (206 + 256)
Gary Johnson (Libertarian) – 0.99% – 5 EVs
Jill Stein (Green) – 0.36% – 1 EV
2008
Barack Obama (Democrat) – 52.93% – 651 EVs (365 + 286)
John McCain (Republican) – 45.65% – 420 EVs (173 + 247)
Ralph Nader (Independent) – 0.56% – 3 EVs
Bob Barr (Libertarian) – 0.40% – 2 EVs
2004
George W Bush (Republican) – 50.73% – 560 EVs (286 + 274)
John Kerry (Democrat) – 48.27% – 513 EVs (252 + 261)
Ralph Nader (Independent) – 0.38% – 2 EVs
Michael Badnarik (Libertarian) – 0.32% – 1 EV
2000
George W Bush (Republican) – 47.87% – 530 EVs (271 + 259)
Al Gore (Democratic) – 48.38% – 528 EVs (267 + 261)
Ralph Nader (Green) – 2.74% – 15 EVs
Pat Buchanan (Reform) – 0.43% – 2 EVs
Harry Browne (Libertarian) – 1 EV
1996
Bill Clinton (Democratic) – 49.24% – 646 EVs (379 + 267)
Bob Dole (Republican) – 40.71% – 380 EVs (159 + 221)
Ross Perot (Reform) – 8.40% – 45 EVs
Ralph Nader (Green) – 0.71% – 3 EVs
Harry Browne (Libertarian) – 0.50% – 2 EVs
1992
Bill Clinton (Democratic) – 43.01% – 603 EVs (370 + 233)
George Bush (Republican) – 37.45% – 370 EVs (168 + 202)
Ross Perot (Independent) – 18.91% – 102 EVs
Andre Verne Marrou (Libertarian) – 0.28% – 1 EV
As you can see, the only one where it'd change the result is 2000, which is now a hung electoral college. If all the electors vote as they're supposed to, then the election will be thrown to Congress and George W Bush will be appointed President by the Republican-controlled House (the Vice-President is a trickier matter, as the Senate was split 50-50 and the Twelfth Amendment is ambiguous as to whether the sitting vice-president can break the tie in this case – but if he can, Joe Lieberman becomes Vice-President). On the other hand, it's plausible that Ralph Nader may release nine of his electors to vote for Gore instead.