Here is the reason humans will not be going to Mars soon. This site also not listed at the Mars Society:

http://mars.jpl.nasa.gov/2001/lander/meca/

The Mars Environmental Compatibility Assessment (MECA) is a set of instruments designed to investigate hazards on the surface of Mars that could effect human exploration. MECA was developed at the Jet Propulsion Laboratory through NASA's Human Exploration and Development of Space (HEDS) Enterprise.

Originally part of the Mars 2001 Lander (cancelled in 2000) MECA now awaits a ride to Mars and the opportunity to complete its mission. Following delivery of the MECA instrument in September 2000, the MECA project was disbanded though the science team will continue activities through FY2001. Based on current Mars architectures, the earliest flight opportunity for MECA (or a MECA follow-on) will be in 2007.

The NASA planetary protection documents in the link below are among others that seem to be missing from the Mars Society website so here is the link and contents you can find:
http://www.icamsr.org/protection.html

ICAMSR Founder and Executive Director Barry E. DiGregorio has written an article covering the history of planetary protection spanning the years 1959 to 2001 for the August issue of CHEMICAL INNOVATION magazine published by the American Chemical Society. The dilemma of Mars sample return, Chemical Innovation 2001, 31 (8), 24-33. Copyright © 2001 American Chemical Society. This article expresses the views of the author and not necessarily those of Chemical Innovation magazine or the American Chemical Society.
http://www.icamsr.org/protection.html

In June of 2001 the Committee on Planetary and Lunar Exploration, Space Studies Board of the National Research Council has placed online a new 132 page report entitled The Quarantine and Certification of Martian Samples which plainly states that NASA did not have and still does not have an adequate facility to examine Martian soil samples for extraterrestrial microorganisms. The report further states that a proper quarantine facility would have to be like no other on Earth and would take at least seven to ten years to build. However, this report does not address how the Martian soil samples would be delivered from Mars to Earth.
http://www.icamsr.org/protection.html

In August of 2001, the Planetary Society placed online an important series of opinions that originally appeared in their magazine: The Planetary Report. The opinions expressed came from NASA's Planetary Protection Officer, Dr. John Rummel, SETI biologist Margaret Race, and Dr. Kenneth H. Nealson, Director of the Center of Life Detection, NASA/JPL along with others regarding the Mars Sample Return mission and planetary protection.
http://www.icamsr.org/protection.html

Is a Mars Sample Return Mission too Risky? A Public Hearing Case Study by Troy D. Wood, Department of Chemistry, University at Buffalo, State University of New York. In this study is explained the background and arguments for and against Mars Sample Return.
http://www.icamsr.org/protection.html

COSPAR Planetary Protection Policy (20 October 2002) Accepted by the council and bureau, as moved for adoption byt SC F & PPP (Prepared by the COSPAR/IAU Workshop on Planetary Protection, 4/02 with updates 10/02)
http://www.icamsr.org/protection.html

SSB Project 2003 - Preventing the Forward Contamination of Mars
Have we contaminated Mars with robotic spacecraft already? This new study will try and attempt to provide new solutions for sending sterilized robotic vehicles to Mars.
http://www.icamsr.org/protection.html

A Draft Test Protocol for Detecting Possible Biohazards in Martian Samples Returned to Earth (NASA/CP 2002-211842).
NASA has prepared a draft protocol for the testing and evaluation of samples that may be returned from Mars by future missions in its Mars exploration program. This protocol is designed to provide a model method whereby such samples can be tested for possible biohazards that could be present if life exists on Mars. The protocol has been prepared as a draft to guide the development of both a final protocol to accomplish biohazard and life-detection testing, and to aid in the eventual design of the facility or facilities that will be required to accomplish that testing. Public comment on this draft protocol is sought to provide for refinement of the draft and to provide information for future NASA planning efforts.
http://www.icamsr.org/protection.html

Emerging Risk Assessment and Management Controversies in the Mars Sample Return presented to: 27th Annual Natural Hazards Research and Applications Workshop Boulder, CO, 14-17 July 2002.
http://www.icamsr.org/protection.html

Astroenvironmentalism: The Case for Space Exploration As An Environmental Issue
Well, this says it all.
http://www.icamsr.org/protection.html

Safe Passage: Astronaut Care for Exploration Missions
What dangers does Mars present to human explorers who may eventually venture there? Before a human mission to Mars can ever be attempted, we must make certain we have taken all necessary precautions.
http://www.icamsr.org/protection.html