Pollster.com is already one of the leading sites for polling, especially this year’s presidential election.
One thing they have in particular that I found impressive is the ability to chart your own data. Let’s take this chart here for Florida: 2008 Florida Presidential General Election: McCain vs Obama. As for today, it shows McCain 47.9 and Obama 46.4. Now, if you study political blogs like I do, you might want to exclude certain polling results from the analysis. Clicking on Tools > Filter, you could exclude all Internet polling if you felt such polling was inaccurate. (Internet polling for this sample is done by Zogby, who in some circles have a not great reputation). So you de-select Zogby.
Now the numbers shift a little to McCain 47.7 and Obama 46.3.
You could even de-select everyone but a certain poll (e.g. CNN/Time) and see what the result are with that (McCain 48.0 vs Obama 45.1).
Once you are happy with it, you can even embed the graphic on your site.
They have a number of good features on their site, but this one is getting alot of press, and alot of embedding on blogs. A good example of how to drive traffic to your site if you offer a great feature.