Let's start this discussion by looking at the electoral map. Based on the most recent state-by-state polls, three states previously won by Bush may be leaning towards Obama - Iowa, New Mexico, and Colorado. One state won by Kerry in 2004 may be leaning towards McCain - New Hampshire. If this is the case, there is no majority winner in the electoral college vote. Each party will receive only 269 votes, and as such, no President will be named due to the outcome of the election.
The 12th Amendment of the Constitution states that in the case of no majority in the electoral college, the vote for President goes to the House of Representatives, each state receiving only one vote, and similarly a separate vote will be cast for the Vice-Presidency. This means that the party tickets could be broken up, and the representatives will select the party leadership.
What my research has found is that it would not be the current Congress who casts the votes - rather the newly elected Congress. This would potentially give Obama an advantage, as the representatives of each state will have to work together to cast a vote for the state - a heavy loss in Congressional seats by Republicans would ensure that a vote favors the Democrats (could be Obama, could be another compromise Democrat, like Hillary).
Unfortunately, if a state delegation is tied, the votes from that state are uncounted. Below is a map of the 2006 election results, giving an example of which states would be in favor of which candidate, assuming no seats are lost to either party. Unfortunately, it is only a guide, as the house moved seats from some states to Western states growing in population.
If everyone in the House kept their seat, and neither party gained a single seat, Democrats would win: Democrats 28, Republicans 21, Tie 2. Obama wins, 28 votes to 21 (total is 51 because Washington, D.C. is counted as state for presidential elections).
Fortunately, the likelihood of another 2006 style Republican defeat is unlikely. The most important point to note is that Republicans must win in key states, where a vote would come down to one vote or a tie - turning the votes in favor of the Republican Candidates.
Stepping back from this scenario, it is dangerously clear that two states are in play for 2008 at this time: New Hampshire (where current polling gives Obama a 0.3% lead) and Colorado (where current polling gives Obama a 1.0% lead). If New Hampshire follows the suit of the Northeast, electing Democrats, and Colorado is pulled back into the traditional role of voting for Republicans, the crisis is averted, and McCain/Palin wins the election.
Should Colorado and New Hampshire both fall in favor of Obama, Obama wins at 273 electoral votes.
It is evidently clear that Colorado is the key state to both campaigns. The next President of the United States is going to have to set up a condo in Colorado... they can't afford not to!