Survey monkey is really easy and you can set more advanced metrics. I have used it in market research and it has everything you need and you can even do A/B testing for different questions. Good luck!!
This isn't an exact match to your requirement for two-way links, but Zim Wiki will link pages based on keywords and also display all the backlinks to a given page. This is suited to more of a freeform network of text nodes than to a set of pairs of nodes that reference each other. In addition, it supports tags, so that you can apply a tag to multiple pages ...
I did a search for "polls" and found these.
Rather than a specific site, I recommend using a Wiki where everyone can add, change, and share the site equally in a public or private environment. Little effort is necessary to set things up just the way you want them.
Have a look at pbworks.com