Not sure how we missed this, but Gallup has put up detailed demographic cross-tabulations based on the Gallup Daily tracking (that's the survey showing a four point lead for Barack Obama as of yesterday, not the USA Today Gallup poll that applied the "likely voter" screen and has been a source of controversy this week).
Here are descriptions and links just received via email from Gallup:
Gallup now has available online extensive data breaking out support for the presidential candidates within demographic, partisan, ideological, and regional subgroups.
The data are updated each Wednesday -- based on more than 6000 Gallup Poll Daily interviews conducted each week – and available here: http://www.gallup.com/poll/election2008.aspx. Importantly, the analyses can now be trended back through the week of June 9-15, showing the pattern of support within subgroup across time.