http://people-press.org/2011/07/22/gop-makes-big-gains-among-white-voters/This is a poll of Partisan Identification + Lean Identification rather than direct voting preferences, but is still interesting to look at.
Basic summary:
Millennial Whites are now roughly as Republican as their elders at +11R, representing an 18-point shift from 2008 where they were D + 7.
Overall, Millennials are still the most Democratic group, but by less than half the margin from 2008, D+13 vs D+28.
Poor (<$30,000) Whites are also now Republican-leaning, going from D+15 in 2008 to R+4 in 2011.
Overall, Poor voters are still Democratic, but went from D+34 to D+22. GOP is now tied with middle-income voters and leads by 5 with upper-income ones.
Regionally, the GOP gained the most (overall) in the Midwest and West, going from D+13 to R+1 in the former and D+15 to D+3 in the latter. Democrats still hold a big edge in the Northeast, and hold a small edge in the South.
Republicans gained roughly equally (+9) across all White Christian groups except Catholics, where they flipped the Democrat's D+8 edge to R+10.
The only group Republicans lost ground with is Hispanics, with their Dem advantage growing from D+38 to D+42. Interestingly, both parties lost identification with Hispanics; Republicans just lost more. However, the 2010 exit polls suggests that while Hispanics may not like calling themselves Republicans, they're still willing to give the GOP a decent chunk of their vote.
And Finally, this means that the Democrat's identification edge overall has dropped from D+12 to D+4. Most of these gains came gradually from 2009-2010, and the totals have been roughly stable since January 2011.
EDIT: The other interesting thing is that all these gains come from Independents saying they lean Republican rather than self-identifying more as Republicans. The number that call themselves full Republicans is unchanged from 2008 (28%), but the number that identify as lean-Republican went from 11% to 16%. The number of Hard-Democrats went from 38% to 34%, and the number of lean-Democrats stayed flat.