Simple LinkedIn PHP is a library for interacting with the LinkedIn API. The library was designed and tested for PHP 5.2+ and is not expected to work with PHP 4. The only prerequisite for Simple LinkedIn PHP is the PHP cURL library.
n0tice is a simple location based public notice board system. It's completely open and unfiltered, and allows users to post any sort of notice they want, tagged with their location, and lets them read notices near them, sorted by distance. Quite a simple little idea, and if it gets a user base, it could end up being quite useful. Although first designed for iPhone, the n0tice API was quickly released to allow integration into other programs, including desktop apps.
Twitter has added alt text support to Twitter Cards and the Twitter REST API. Alt text is an important piece of metadata for those who are visually impaired as screen readers and browsers use alt text to explain to visually impaired users the content of each image on a web page.
How does the Web's largest ticket search engine improve its API? By giving developers easy access to more information, of course. SeatGeek recently made links to artists' Spotify and Last.fm profiles available through the SeatGeek API, and the company promises even more data in the future.