I like this one because it is done jointly by a Republican and a Democrat, and because I like the Tarrance Group.
Most interesting number to me is that nearly 50% of those surveyed believe strongly that the country is off on the "wrong track." This is, IMO, the most important indicator of how an election is going to go for an incumbent. Lots of other interesting things too, but I'll see what people are most interested in before commenting further.
http://www.tarrance.com/pdf/9701Q.pdf
For analyses, see:
http://www.tarrance.com/pdf/04DemocraticAnalysis.pdf
http://www.tarrance.com/pdf/GOPAnalysis.pdf
And if you want user-friendly charts, try this:
http://www.tarrance.com/pdf/9701BGCharts.pdf