Panzer General Series

The Battle Group
Offers an international membership from more than 30 countries. Competitive playing formats for WW2 scenarios and campaign simulation.
http://www.ggholiday.com/bg/

Builders Paradise
Offers maps, scenarios, campaigns, and equipment information.
http://www.strategyplanet.com/panzergeneral/

Herr General
Offers scenarios.
http://www.herrgeneral.de/

The PanzerStef PG2 site
Information, tips, custom scenarios, and campaigns. Also, includes tips for PG3D.
http://pagesperso-orange.fr/stephane.grateau/

The 5 Star General
Features campaigns, scenarios, utilities, equipment files, patches, and links.
http://www.peachmountain.com/5star/

Tortoise Page
Offers custom scenarios and campaigns.
http://www.fortunecity.com/meltingpot/oxford/285/tortoise.html