The Site User List module displays a sortable and searchable list of all the users on the site based off of their profile.module fields.
Which fields are visible can be configured, both by the admin (who choses which fields are available) and the user (who chooses which fields are displayed). The list can be searched.
2009 Jun 24: Drupal 6 beta version available. Sorry it's taken so long...
2007 Jun 25: if the data from fields on your registration form is not showing up in the listing, please see http://drupal.org/node/138915 . This is a bug in Drupal, not in Site User List. There is a patch available which fixes this problem.