We are going to be moving images to a new domain (twimg.com) to streamline our image hosting and offer better performance. We hope this will have limited impact as will only change the image URL. Example URLs include:

Profile images:

http://s3.amazonaws.com/twitter_production/profile_images/35240332/2929920.gif

http://a0.twimg.com/profile_images/35240332/2929920.gif

Background images:
http://s3.amazonaws.com/twitter_production/profile_background_images/18156348/jessica_tiled.jpg.jpeg
http://a0.twimg.com/profile_background_images/18156348/jessica_tiled.jpg.jpeg

[ed: no word on when this will happen yet]

(announcement thread)

The documentation for the /search method specifies that all queries should be performed with an HTTP GET. On or after July 15, 2009, we will begin enforcing the use of HTTP GET for all queries. Requests sent to the /search method which are not performed with an HTTP GET will be met with an HTTP 403 response. (announcement thread)

Feature (REST): The rate limit has been changed form 100 to 150. (documentation)

Feature (REST): API updates are now identified as being from API rather than web.

Fixed (OAuth): Allow international domain names for OAuth URLs via punnycode input. (issue 772)

Fixed (OAuth): The oauth_access_type parameter was not respected in all cases. (issue 767)

Feature (Search): Added Farsi/Persian to the list of available languages.

Fixed (REST): The new friendships/show method no longer returns 502 on large users. (issue 757)

Fixed (Search): Searches for accented and non-accented words are now combined. (issue 503)

Fixed (Mail): Improved outbound email reliability (for apps parsing DM/friend emails)

Fixed (REST): The JSON returned in maintenance mode now correctly contains null rather than NULL (issue 703)

Fixed (OAuth): Improved error handling when invalid data is submitted in place of a token.

Fixed (OAuth): Added a more helpful error message when you try to use a request token in place of an access token.

Fixed (REST): Partially fixed issue with tiling background images via the API (issue 650)

Feature (REST): Added new friendships/show method (issue 474, documentation)

Feature (REST): Added screen_name and user_id attributes to direct_messages/new for disambiguation (issue 550, documentation)

Fixed (Search): The combinations of some operators with since_id incorrectly returned an error, now it returns results. (issue 742)

Fixed (Search): Searches for never-used phrases incorrectly returned an error rather than 0 results. (issue 740)

Fixed (Search): Search errors are now returned in the API format requested (issue 509)

Feature (OAuth): Updated OAuth to 1.0a and added a PIN-based desktop workflow for OAuth apps. (announcement)