(Syahir and Mods, please feel free to edit and add content accordingly)
There's been some talk recently in the forum of creating a sticky thread containing links to helpful resources for beginners. Here is the beginning of this endeavor...
I would first strongly suggest visiting the W3schools.com website. We really don't need to add any other resources than that. It's the ultimate guide to learning website structure, code, and css. They also provide examples you can manipulate (real-time) to practice.
** Graphene Wiki **
The Graphene Wiki is a great place to find more information about each of the options menus found in Graphene.
** WordPress Codex **
The WordPress Codex contains informational articles, forums, a plugin repository, and an online manual for installing and using WordPress.
** Graphene Theme tutorials **
A few blogs about customizing the Graphene Theme.
** Child Theme **
A child theme is extremely important when performing advanced CSS and PHP with the Graphene theme. Anytime you want want/need to make a customization outside of the admin options panel, it is best to do it in the child theme. Check the resources below for more information on how to implement a child theme.
** HTML **
HTML Dog has a nice beginners breakdown on basic HTML usage.
** CSS **
Again, HTML Dog seems to be a popular second best to W3schools.
One of the best kept secrets on the web is Mozilla Firebug for the Mozilla Firefox web browser. Check it out!
Having the Mozilla Firebug extension for Firefox is imperative for working with CSS.
** PHP **
Here is a fantastic tutorial covering the basics of PHP. It is written in .pdf format so it's very easy to save to your computer or print for reference.
** Graphics **
CSS gradients beautiful and add a nice, subtle touch to any area. Here is a great tool for generating the CSS code for different types of gradients.