United Food and Commercial Workers, Canada

The union that's organizing Wal-Mart stores in Canada has a site for Wal-Mart workers to learn more:

http://www.walmartworkerscanada.com/ [1]

International Labor Rights Fund

ILRF is organizing campaigns to change Wal-Mart's supply chain practices, including spearheading a legal action by Wal-Mart supply chain workers claiming massive, systematic hours and wage violations.

http://www.laborrights.org/projects/corporate/walmart/index.html [2]

Major US campaigns against Wal-Mart

There are two major US-based campaigns trying to change Wal-Mart's practices on a whole range of issues. Find out more at:

Wake Up Wal-Mart: http://www.wakeupwalmart.com [3]
Wal-Mart Watch: http://walmartwatch.com/ [4]

UK campaign on ASDA/Wal-Mart

Similar to the US campaigns, a website dedicated to ASDA, Wal-Mart's UK subsidiary
http://www.asdawatch.org/ [5]

Also, check out the Alternative Report on ASDA Wal-Mart, available at:
http://www.waronwant.org/download.php?id=369 [6]

Campaign for Labor Rights

http://www.clrlabor.org/campaigns/wal-mart/wal-mart.htm [7]