WPbeginner has done a great job of rounding up all the proposed features for WordPress 3.1. In a nutshell, we can look forward to:

• internal linking
• admin bar (similar to WordPress.com)
• ajax admin
• separate network dashboard
• quick press template tags
• UI improvements for themes
• post templates
• cool taxonomy tweaks

If you want all the details for these features head over to WPbeginner.com. The 3.1 release date is mid December.