BP Better Directories is a new BuddyPress plugin that will turn your (kinda boring) member directories into something a lot slicker. Site admins select which fields they’d like to be filterable in member directories. Site visitors can then use a nice AJAX interface for narrowing search results.
This plugin is being developed for the CUNY Academic Commons, and is in early beta. Don’t use on a live site. There’s also a pretty good chance that the technique I’m using in the guts of the plugin won’t scale all that well without proper caching. You have been warned! (Also, it requires at least BP 1.5.1.)