Here is a little report card on the polling organizations from Survey USA. It shows the average median error of polling organizations that conducted polls, within seven days of a presidential primary election. The lower the number, the more accurate the polling organization has been.
I do not particularly like the market being flooded with polls prior to elections, because I think they can persuade some voters from voting. If their candidate is way behind in a pre-election poll, they may just think their vote will not count and blow it off altogether. If the poll is skewed, if enough people see it and do this, it effects the election.
But, no one cares what I think. So, poll they do. At least this gives us an idea which polls are more likely to have the more accurate information.
Check it out, when you get a chance.
For what it's worth, here is Survey USA's average mean error report.