Reading the internals of several polls together, most of the remaining undecided voters are white, older voters who went heavily for Bush in 2004. There also seems to be a smaller but perhaps significant chunk (depending on which state) of Hispanic Catholics who also favored Bush in 2004.
So at a minimum (just based on race) we can expect these voters to break 60-40 for McCain. When you factor in their previous ideological leanings (voting for Bush vs. Kerry), it looks very good for the Arizona senator.
The Hispanic undecideds would appear to be more fertile territory for the Obamessiah, but the more frequently they go to church services the less likely they'll be to vote for a Dem.