Much of this is taken from the Specialist Games website, which I would recommend visiting to obtain the latest information. What I am aiming to with this section of the site is to make available the pdf's released by Games Workshop along side rules collected over many years of playing Necromunda.
The Necromunda rulebook is available as a free download from the Specialist Games website.
Resources Necromunda Roster - Pete A
Available in both A4 and letter paper formats (MS Excel format) Gang Roster - Brett DeWald
An alternative roster sheet which has slightly different imformation on it (MS Word format) Weapons Summary Sheet - Brett DeWald
Includes outlander weaponary (MS Excel format) The Necromunda Card Game Project
The concept behind the Necromunda Card Game is to supplement the rules and gameplay of Necromunda by adding a card game element. These cards can be played during the standard Necromunda turn sequence, and have an immediate effect on the game.
This allows for more variety and unpredicability in the game. You can interfere with your opponent's turn, or cause your models to perform heroic actions to accomplish an objective.
Games of Necromunda using slightly different rules systems Necropolis: Armageddon! - Robin Whelan
Set in the burned-out ruins of Hades hive, Necropolis allows players to take command of a small band of warriors and fight for their lives against the other denizens of the dead city. Whether you fight as the invading greenskins, stranded Guardsmen or low-down scavvy renegades, you will find all the danger you can take and more besides in the smouldering wreckage of Ghazghkull's brutal revenge.
Necromunda: Millennium Edition - Robin Whelan
Whilst using the same background, Robin has attempted to bring a greater level of realism to Necromunda. Models act as individuals much like as in Inquisitor, and the weapons don't have a maximum range. The links on the page appear to be broken but in actuallity if you look at them you will see replacing any / with \ fixes the problem. It is well worth a read.
Nazimunda (pdf format) - Steve Lee
This WWII varient of GW's Necromunda, whilst not a full rendition of the Necromunda rules for a WWII setting, this document is a collection of rule variations
that allow Necromunda to be played in a WWII setting.
Ancient Battle Necromunda Cross - Kevin McLean
A WAB Skirmish game based around Saxon/Viking encounters that makes use of the Necromunda game mechanics.