I came across an interesting web tool today that I thought might be a good fit if you have a website with a search engine. The tool is called a Swicki. It's like a Wiki, but used for search.
According to their website: "Swickis are a cross between search engines and Wikipedia - the community can add, delete and improve the results."
From what I read on their website, it looks like the search engine brings up results based on what other visitors of your site have searched for. So the results are then uniquely relevant for your community. Once the results are shown, you can also vote for or against the results.