Please select a link from the list bellow. This is a collection of links that I use myself, and as such it represents yet another look into how my mind works ;)

KDevelop

My IDE of choice. It's built for use with KDE and runs under that... And really nicely too I might add! The version that is being worked on now (codename Gideon) will be released with KDE 3.2 later this year and is proving to be even better than the original (it's what I'm using p.t.)

Planet Sourcecode

Quite possibly the world's largest code repository. Currently supports: VB, Java and JavaScript, C and C++, ASP/ VbScript, SQL, Perl, Delphi, PHP, Cold Fusion, .Net and LISP.

www.php.net

The PHP homepage. Contains, amongst other things, a community annotated version of the PHP Manual. Very much worth a first look when searching for solution ideas for PHP.