The subject being discussed makes some difference though. A search functionality in a programming related forum is fundamental, while it probably isn't in a music one for example.
I've been running a music forum since 2001 (millions of posts) and I'm not sure an implementation of this type would suit... but these are all good concepts overall.
it might be some swfsheet (http://www.bit-101.com/blog/?p=2948) type of software. Having that sprite (what a design!!!), you can animate it with jquery easily...