This page lists useful tools for players and GMs.

Random Generators

Abulafia Random Generators includes tons of random names, descriptions, prophecies, etc.

Random City Map Generator creates a reasonable top-down map of a medieval-style city, complete with roads, rivers, a possible port, etc. The drawing is simple, but the towns always look realistic.

Seventh Sanctum also has a number of generators.

What's behind this door? Help's generate rooms on the fly.

Lists

John Kim's Free RPG's on the Web lists over 500 free RPGs.

Onomastikon is a huge list of names from around the world, grouped by civilization.

Maps

101 Fantasy City, Town, and Village Maps is exactly what it claims to be.

Parasite Designs Offers oodles of Creative Commons released black & white dungeon maps.

Online Tools for Any System

D&D 4E Online Tools

Online Tools for Other Systems

Articles for Players

Articles for Game Masters

Articles for Freelancers

D&D 4E Options (Rules, Powers, Themes, Classes, etc.)

Open Source Monsters

Open Source Items

RPG Design

Free Adventures

Orc and Pie, D&D 3.5/Pathfinder. Also see the web enhancement and the D&D 4E skill challenge version

Free Settings

Game Reviews

Actual Plays

Articles About D&D As Phenomenon (Edition Wars, etc.)

The D&D 5E "Games Are Dying" Kerfuffle

D&D Next

Regular Roundups

Everything Else