We have just released filter.js which is a jQuery / JSON based search result filter.
It is mustache.js compliant and we have used it successfully in a few Rails portals.
Posting to the group because I believe it will help others too.
The blog post for this is at http://blog.joshsoftware.com/2011/09/28/filter-js-client-side-search-filtering-using-json-and-jquery/
Its recently also launched on SoftPedia http://webscripts.softpedia.com/script/Forms-and-Controls-C-C/Filter-js-71265.html
Do check it out!