Filterable List Plugin – Is there one out there?

Hi All.

I’m just setting up a wordpress site, and I’m after some functionality which will be core to the site.

I require a filterable list, which refreshes (either live or every 20 seconds or so) where users can add their own listing.

There will be no e-commerce functionality, just a plain listing site, where users can check in to find listings using filters or list their own listing.

Anybody know the best solution to this either through a plugin or WordPress functionality?

Thanks!