A couple of things to note. It is often difficult if not impossible to predict which state will actually "swing" in any election. Historical analysis shows that the swing state map tends to change dramatically in cycles of about every three presidential elections.
Also, in election cycles in which there is a general "kick the bums out" mentality among the electorate, it is doubly hard to predict swing states. This is a time when the out of favor party can often lose even in traditional strongholds. It is a very good opportunity to make inroads, in this case, for the Democratic Party to make inroads in states that have been voting Republican.
Most of the analysis that I've seen tends to discount the importance of the African American and Latino vote and concentrate mostly on "white working class" voters. I think this is a big mistake.
African American turnout has historically been important for Democratic success in presidential elections for some time now. States like Florida and Michigan often hinge on the turnout out of African Americans.
Two states not often mentioned as swing state possibilities are Louisiana and North Carolina, both potential Democratic wins depending on African American voter registration and mobilization.
We also cannot forget the anti-war crowd when studying voter demographics. This group could also benefit Democrats in states like Oregon, Virginia and North Carolina. Remember Jim Webb won in Virgina on a platform that opposed the Iraq War.
Then there are those states are traditionally Republican but have Democratic governors and/or senators. Many of these are totally ignored in swing state discussions. They include Kansas, Nebraska and even John McCain's home state of Arizona. Obviously there are burgeoning Democratic or Democratic-Independent movements in these states or no Democrat could win in a statewide election. Even if the nominee can not win in these states, I think it is necessary to campaign hard in them.
By fighting in these states, not only do you grow the movement, but you keep the Republicans on the defensive. The latter will definitely recognize the potential dangers of losing old strongholds. In the end, also there are always a certain percentage of people who only get motivated when they see things getting done on a local level. They will not buy into the idea that they're states do not count and that they should contribute money only to help in the national effort. This is no problem with the Obama campaign as Barack Obama has roots in community organizing. In the end, this development at the local level ends up netting more also at the national level as I think is demonstrated by Barack's record-smashing fundraising efforts mostly collected from small and first-time donors.