One of the biggest strengths of PHP is its "glue" power. Take any C library and with a little magic and a compiler you have a fantastic extension. These extensions hide in PECL, but few people can tell the good from the unmaintained or just plain broken. Find the best extensions for your project, learn about PECL, and find out how to become a part of the PECL developer community.
Clipping is a handy way to collect important slides you want to go back to later.