Want to contribute

Hello I am a senior developer currently employed in a digital agency working on the usual e-commerce solutions. In the past I have done extensive work in 'c' so I would like to contribute to the PHP source, I don't mind what tasks whatever they need help with bug fixing would be a good start. This is my first open source contribution and I am a bit confused about the mailing lists, I was using the web interface at http://news.php.net and I could not find where to post a message or work out what mailing list would be relevant. Please be patient with me it is the first time I have contributed to open source so I am not familiar with the lines of communication. Thanks Nicholas