wordpress 3.3 is released on 12th Dec 2011. This is next biggest release of 2011.
Highlights
Easier Uploading
File Type Detection – A single upload button
Drag-and-Drop Media Uploader
Dashboard Design
New Toolbar in the dashboard, combining the Admin Bar and admin header
Responsive design for some screens, including iPad/tablet support
Flyout menus, providing single-click access to any screen
New User Experience
New feature pointers, helping users navigate new features
Post-update About screen
Dashboard welcome area for new installs
Content Tools
Better co-editing that releases post locks immediately
Don’t lose widgets when switching themes
Tumblr Importer
Under the Hood improvements
Use the postname permalink structure without a performance penalty
Improved Editor API
is_main_query() function and WP_Query method
Remove a number of funky characters from post slugs
jQuery 1.7.1 and jQuery UI 1.8.16
A new Screen API for adding help documentation and adapting to screen contexts
Improved metadata API
Performance improvements and hundreds of bug fixes
User Features
GENERAL
Admin doctype changed to HTML5 (#18202)
Show Toolbar in backend by default (#17899)
Drag and drop multi-file uploading (except older IE)
Fix Press This editors
Switch admin menus to flyouts from dropdowns
WebMatrix support
Improve cron locking; avoid multiple cron processes looping over the same events
Add pointers feature, and pointer to admin bar
Introduce help tabs and WP_Screen
Style tweaks to the update nag
DASHBOARD
Ensure text in the dashboard recent comments widget wraps up properly
POSTS
When inserting a Gallery to be ordered by Date/Time use the post_date field for ordering rather than ID
Rename ‘Post Tags’ to ‘Tags’
Make DFW (Distraction-Free Writing) content width match exactly the reported width from the theme
Improve the image drag-resize detection in the visual editor (supported in FF and IE only), remove the size-* class if the image is soft-resized
Add TinyMCE command to handle opening of the upload/insert popup, fix the shortcut “Alt+Shift+M”, fix the “image” button in DFW
Allow Apostrophes in Post Passwords
Add post formats to quick edit and bulk edit
Hide post title field in DFW if title is not supported by the current post type or missing
Clean up remnants from having negative Post_ID
MEDIA
Merge media buttons into one
Add the styling for “drop area” to Media->Add New
Add support for rar and 7z file uploading
LINKS
COMMENTS
Use WP_Editor when editing or replying to comments
Use ‘View Post’ instead of ‘#’ for view post links in comment rows
APPEARANCE
Use the Settings fields/sections API in Twenty Eleven
Load all Parent theme stylesheets before Child theme stylesheets in the TinyMCE Editor
Clean up Plugin/Theme uploads after successfully installing them
Improved Theme upload and validation
Avoid losing widgets when switching themes
Make Distraction Free Writing content width match exactly the reported width from the theme
Allow current_theme_supports() to be used to check for specific post formats
Improved Menus
Contextual help for Twenty Eleven theme options page
PLUGINS
Improved Plugin upload and validation
Stop remembering the last viewed plugins screen; always show all plugins when returning to plugins.php
TOOLS
Add the Tumblr importer to the Importers List
Add wxr_export_skip_postmeta filter for skipping postmeta in exports
USERS
Removed user option to disable Toolbar (admin-bar in 3.2) in the Dashboard
SETTINGS
Add postname to Settings > Permalinks and remove the help text talking about permalink performance; make the slugs (and /archives/ rewrite base) translatable
Clarify Settings > Privacy
Use title case in Settings > General
Disallow indexing wp-admin and wp-includes in robots.txt
INSTALL PROCESS
MULTISITE
Allow creating sites with IDN domains
Move network/settings.php POST handling out of network/edit.php
Dissolve wp-admin/network/edit.php
Add ‘Network Enable’ link after installing a theme in the network admin
Use update_blog_details() in wpmu_update_blogs_date()
Change Network Settings to just Settings
Implement bulk update for network/themes.php
Fix inviting existing users to a site with email confirmation
Check for plugin/theme updates every hour when hitting update-core.php, not just themes.php/plugins.php
