The company I work for is sponsoring a code competition for a new open source application we just released, Shine Live Help. It isn't an exclusive php-competition, but php is a personal preference of most of our staff and what we use so we'd like to see a lot of php contributions.
The "official" blurb:
iRadeon is sponsoring a code competition for its new GPL application, SHINE Live Help. The SHINE Code Prix starts February 9th through March 11th. The goal of the competition is to improve usability, innovation, and interoperability with open source projects. Any programmers interested in participating can register and find more information at www.iradeon.com/codeprix.html
MOD EDIT: Edited for AUP compliancy... if you want to know more information, DMG, you may PM me (and hopefully I'll remember :p).
