The New York Times has a great tool for comparing vote patterns among a few basic demographic groups going back to 1980. Here are a few patterns that stand out:
Women: Obama won women by 13% over McCain. That is the second largest gender gap since 1980 (only Clinton's 16% advantage in 1996 was larger).
Men: The national exit poll currently shows Obama with a 1% edge over McCain among men. The only other Democrat to win men since 1980 was Bill Clinton in 1992. But that was in a three-candidate race, so Obama's share of the male vote (49%) was the highest for any Democratic candidate during the last eight presidential elections.
African Americans: African Americans made up a larger share (13%) of the electorate than they had in any of the past eight presidential elections. In addition, Obama won 96% of the black vote whereas previous Democratic nominees failed to do better than 90%.
Hispanics: Hispanic voters continued a pattern that began in 2006 by renewing their strong support for Democratic candidates. Obama captured two-thirds of Hispanic voters, who made up 8% of the electorate.
Young Voters: Obama won two-thirds of the 18-29 age group. This is the fifth straight presidential election that Democrats have won the youth vote. However, Obama's margin with this group is substantially greater than any previous Democratic nominee. In fact, no candidate has won any of the standard exit poll age groups by as big a margin as Obama won the 18-29 vote in this election.