This is a summary of recent technology and site configuration changes that affect the English Wikipedia. Please note that some bug fixes or new features described below have not yet gone live as of press time; the English Wikipedia is currently running version 1.26wmf20 (cc643a0), and changes to the software with a version number higher than that will not yet be active. Configuration changes and changes to interface messages, however, become active immediately.
The ability has been added for oversighters to unhide a username (reversing the hide-user feature) when unblocking an account; Previously, it was only possible to reverse the hide-user action by reblocking the user with the hide-user setting unchecked. Also, when unblocking and unhiding a user, the hidden edit summaries can now be restored. (r49685, bug 18543; bug 18542)
When purging an image page, the metadata now will also be purged. (r49848, bug 18571)
MediaWiki Exif handling now properly handles tags that are arrays, such as GPS coordinates. (r49677, bug 13172)
Subversion revision numbers for MediaWiki extensions are now shown on the Special:Version page. Revision numbers previously displayed were oftentimes inaccurate, but changes made will have the revision numbers automatically update now and show accurately on the Special:Version page. (r49890, bug 18242)
Developer Andrew Garrett (User:Werdna) has restructured the MediaWiki code used to manage user preferences, which are now managed using a class and is separated logically from the user interface code. Along with the changes, the GetPreferences hook is now available (and must be used by) MediaWiki extensions to access and add user preferences. The code has been rewritten to be more efficient; Wikipedia users should not see any difference. 
The TorBlock configuration has been changed to require explicit block exemption, rather than allowing all logged-in users to edit via a Tor proxy. The change is due to the amount of harassment and vandalism problems coming in via Tor proxies, which substantially overweighs the amount of positive contributions via Tor. 
The Google Summer of Code projects for Wikimedia have been announced: Niklas Laxström (User:Nikerabbit) will be working to improve localization and internationalization, Zhe Wu will work on an image thumbnailing daemon, Gerardo Antonio Cabero will be improving the Cortado Java applet for playing videos, and Jeroen de Dauw will be improving the Semantic Layers extension and integrate it with the Semantic Google Maps extension. 
The pywikipedia mailing lists have been restructured and split into multiple lists, with bug reports now sent to the pywikipedia-bugs list, svn updates to pywikipedia-svn, announcements to pywikipedia-announce, and general pywikipedia discussion on pywikipedia-l.