Does anyone know of a good example of an advanced filtering funtion on a web app?
Something with functions like Greater Than, less than etc?
Airline sites... http://www.kayak.com/ etc
There are many examples of websites with functional, but overwhelming filtering options, like this 'Phone Finder'.
These filters are hard to use, because they don't give immediate feedback about the effect of a filter choise and because they don't give insight in the relation between filters.
In this B2B webshop users can filter the search results on two related variables: the number of items they need and the amount of money they want to spend. Adjusting a filter has immediate, visual effect on the search results.
YohanYlab, designers for interactionwww.ylab.nl
A little bit niche, but try http://carzone.ie for filtering. Some clever tricks there, I particularly like the bar graph + slider approach.
MC master shows how useful speed is to progressive filtering