For each exposed filter's parameter, this code will calculate and display the number of results that will be displayed if chosen.
This only currently works for Taxonomy filters. If you want to see where the newest hotness is at, checkout the vdc_ajax_loader branch. That branch works best at the moment but the jQuery selectors are written for the checkbox markup generated by the Better Exposed Filters module http://drupal.org/project/better_exposed_filters
Some doubted this could be done effectively with Views under heavy load and large amounts of data but it's working out quite well at http://www.edutopia.org/schools-that-work. This is a much cheaper solution than Apache Solr. Feel free to contact me if you need help with implementing this.