As Troutman says, polls are pretty much meaningless because they provide a (possible) snapshot of the entire country's popular vote at a single point in time. More relevant are the electoral college polls which try to predict how individual states might go and who might win on that basis (remember in 2000, Gore won the popular vote but lost when George W. Bush was awarded Florida's electoral votes by the US Supreme Court.)
A few sites that are good at tracking electoral vote polls (but which can also show pretty wild swings if you look at their history/trend pages since some of them only add latest poll data as definitive and don't aggregate it ie. if Bush polls winning in Florida today but Kerry has for the last three weeks, they give Bush Florida in today's map):
Electoral-Vote.com - as of today has Bush up 307 to 211 (270 needed to win)
(
http://www.electoral-vote.com/carto/sep17c.html also has a map that shows the states sized by the weight of their vote, not their geographical size (ie. New York is huge, North Dakota is small))
Race2004.net - has Bush up 216 to Kerry's 209 with 113 "undecided" (ie. too close to call)
Daily Thoughts has Bush up 202 to 175 and, if you count close ones, Bush wins 291 to 233.
Larry Sabato's Crystal Ball has Bush up 284 to 254.
Poll Watcher has Bush up 330 to 208.
If anything, I think the numbers above show that like polls, electoral vote predictors will also vary widely and also like polls, they are a single snapshot on a single day (or whenever these polls were last updated.) I check these sites regularly and have seen Kerry with a big lead, I've seen them at a dead heat in electoral votes as they are in polls, and I've seen Bush with a big lead.
There's still a month and a half to go until the election and the only thing that's really important is which lever people pull in November (or which button they push on those new electronic voting machines. Er, hopefully that matters!)
Here's the
MetaFilter Thread where I first heard about most of these sites (except Electoral-Vote.com) and some interesting back and forth commentary about the topic.
Whoever you like for the election, I think the best thing to hope for is a decisive win by one candidate or the other. If the US has a 2000 all over again where the election is decided by one state and anywhere from 80 to 1000 (I think the official count is ~500) votes, there could be big trouble. This 50-50 partisan split in American politics could become a permanent thing with no hope of ever healing so that the two sides can at least talk to each other without the hatred and loathing we see now.