Here are some links to DnD things I've found useful:

References:
-Official DnD 3.5 Edition System Reference Document (SRD): The SRD has all the information from the three core rulebooks of DnD and is open material under the Open Gaming License(OGL). This is Wizards of the Coast's version of the SRD which is available as multiple PDF files free for download.
-Unofficial DnD 3.5 Edition System Reference Document (SRD) by theraven and stephenh: This version of the SRD by stephenh and theravern is presented as a web page for easier referencing without having to download large PDF files.
-Unofficial DnD 3.5 Edition System Reference Document (SRD) by Sovelior and Sage: Another online version of the SRD by Sovelior and Sage, though this one has a much more crisp and clean look to it and easier navigation.
-System Reference Documents: The hosting site for online SRDs, you can find downloadable versions here as well as SRDs for 3rd edition and d20 modern.

Legal:
-Open Game License v0.1: For reference concerning the SRD. As of yet, Iridethian matierial has -not- been deemed Open Game Content.

Resources:
-Irony Games' Dice Server
-Random Number Generator
-Emanuele's Character Sheets: In Adobe PDF format.
-Automated 3.5 character sheet: Enter the info and it will calculate everything for you. Then just put your e-mail in the box at the top and it will send you a copy of your character sheet in PDF form.
-3.5e Character Sheet: The beauty of this one? It's in Word format for easy editing and saving. Great for online games!

Keep an eye on this topic for more useful links, and if you have any to add, PM them to me
-Draggy