Drupal released their first beta of the next version of Drupal called 5.0
Some significant changes including a new core theme and a web installer for making it easier to install Drupal. Lots of performance updates too!

http://www.drupal.org

completely retooled the administration page

• /admin now contains an administration page which may be themed
  
• reorganised administration menu items by task and by module
  
• added a status report page with detailed PHP/MySQL information
  

added web-based installer which can:

• check installation requirements
  
• automatically generate the database configuration file
  
• install pre-made 'install profiles' or distributions
  
• import the database structure with automatic table prefixing
  be localized
  

System

• added new default Garland theme
  
• added color module to change some themes' color schemes
  
• included the jQuery JavaScript library 1.0.2 and converted all core
  

JavaScript to use it

• introduced the ability to alter mail sent from system
  

module system:

• added .info files for module meta-data
  
• added support for module dependencies
  
• improved module installation screen
  
• moved core modules to their own directories
  
• added support for module uninstalling
  
• added support for different cache backends
  
• added support for a generic "sites/all" directory.
  

usability:

• added support for auto-complete forms (AJAX) to user profiles.
  
• made it possible to instantly assign roles to newly created user accounts.
  
• improved configurability of the contact forms.
  
• reorganized the settings pages.
  
• made it easy to investigate popular search terms
  
• integrated urlfilter.module in filter.module
  

block system:

• extended the block visibility settings with a role specific settings.
  
• made it possible to customize all block titles
  

poll module:

• optionally allow people to inspect all votes.
  
• optionally allow people to cancel their vote.
  

distributed authentication:

• added default server option.
  
• added default robots.txt to control crawlers.
  

database API:

• added db_table_exists().
  

blogapi module:

• 'blogapi new' and 'blogapi edit' nodeapi operations.
  

user module:

• added hook_profile_alter().
  
• e-mail verification is made optional.
  
• added mass editing and filtering on admin/user/user.
  

PHP Template engine:

• add the ability to look for a series of suggested templates.
  
• look for page templates based upon the path.
  
• look for block templates based upon the region, module, and delta.
  

content system:

• made it easier for node access modules to work well with each other.
  
• added configurable content types.
  
• changed node rendering to work with structured arrays.
  

performance:

• improved session handling: reduces database overhead.
  
• improved access checking: reduces database overhead.
  
• made it possible to do memcached based session management.
  
• omit sidebars when serving a '404
  
• Page not found': saves CPU cycles and bandwidth.
  
• added an 'aggressive' caching policy.
  
• removed the archive module.
  

upgrade system:

• created space for update branches.
  forms API:
  
• made it possible to programmatically submit forms.
  improved api for multistep forms.
  

theme system:

• split up and removed drupal.css.
  
• added nested lists generation.
  
• added a self-clearing block class.