An online book (or $2.99 pdf) on learning python. Looks interesting. Smart name.
An HTML entity lookup service. Type in part of the name or character and it'll show you the options. Useful.
Wicked site to generate HTML5 boilerplates or starting points from which to design stuff. includes bootstrap, Google Analytics, and loads more stuff. Very, very useful.
Excellent article describing in depth how to have PHP store session data in memcached and the differences between the memcache and memcached implementations in PHP. Very useful.