This is a list of links that are VERY useful regarding DnD core rules. Feel free to add to it whatever you feel is helpful.

• d20 System Reference Document: The d20 system reference document is essentially the complete core DnD rules (and some supplementals), laid out by Wizards of the Coast and free for anyone who wants to view them. Complete with inter-page links and a search feature for quickly finding any rules you may need. It's quicker, easier, and uses less paper than a PHB.

• Automatic Character Sheet: Comes from the page above. A PDF file for helping calculate the numbers on your character's sheet. Simply insert your ability scores, and it practically does the rest for you.

• Crystal Keep d20 Index: ** An extremely comprehensive set of official DnD and d20 rules from multiple sources, arranged by category as a set of PDFs.