Andrew Nacin writing on the WordPress.org blog, says The second release candidate for WordPress 3.1 is now available..
Changes since RC1:
The security fixes included in WordPress 3.0.4
Fix issues related to handling a static front page
Fixes and enhancements for the pagination buttons
Fix searching for partial usernames
Properly reactivate plugins after editing them
Always show the current author in the author dropdown when editing a post
Fixes for attachment taxonomies
Fix node removal for the admin bar
Fix the custom post type show_in_menu argument
Various fixes for right-to-left languages
and other changes
More info and download: http://wordpress.org/news/2011/01/wordpress-3-1-release-candidate-2/