New

• LDAP Group Authentication
• Collectd Monitoring
• Two-factor Authentication
• Mobile Views
• New Gist
• Releases
• Repository Next UI Refresh
• Identicons
• New Explore & Trending Views
• Code Search API
• Checking out Pull Requests
• OAuth Improvements
• Explore Everyone's Stars
• Deleting files on GitHub
• Task Lists in Gist
• Repository redirects
• File Size Limits (note: no pushes are rejected currently)
• Improved Service Hook Backend

Enhancements

• Upgraded git to v1.8.4. This should fix some repository corruption issues caused by git race conditions.
• Removed solr (all searching is now uses ElasticSearch).
• Admin CSV reports are now only cached for an hour (down from 24 hours).

Additional information is available here.