Lets get some google going!

[shea]

Hypertext D20

System Reference Document .ORG

this is new ..
The other Game Company

The old yeller
WOTC D20

The top four results from google there ya go.
Lets keep it going! You know 3.X links peoples
Lessee'em!

[beastman]

have some more:

useful indexes at: www.crystalkeep.com/d20/index.php

spread-sheets: www.nzcomputers.net/heroforge/

dungeon-tile mapper: jai.hordelings.com/dungeontilesmapper.htm

and still some more:

d20 midnight srd/ogl: darknessfalls.leaderdesslok.com/

PC-character-visualizer: www.heromachine.com/

a promising DM-tool: www.adamczak.com/Andy/D%26D/

greyhawk weather forecaster: koti.mbnet.fi/myrpg/rpg/wf/