As I mentioned to anyone who would listen to me during the RNC, please wake me up in two weeks, because the polls were going to cause me angst. Not surprisingly, they did -- John McCain took over the lead in the daily tracker polls. But today, for the first time since the RNC ended, Obama is back on top, 47-45, according to Gallup, which I think is the best one to look at right now (and not just because they have Obama leading!). Since last Friday, Obama has made up 4 points in Gallup, 2 points in Rasmussen, and 2 points in Diageo-Hotline tracking polls.
As for why I like Gallup, they don't correct for party identification, as Rasmussen does. While that could create for volatility in any given one sample, over time (and thus over more samples) variations in response bias will even out. Also, they don't appear to push leaners to decide, which Rasmussen does. As for Diageo-Hotline, they have been doing a tracker for just a few weeks now, while Gallup and Rasmussen have been doing it for decades and years, respectively. Further, their sample size isn't as big, so it tends to be more volatile.