OGame

OGame Tips
Contains tips and strategies for gameplay. Also has tools, tips for getting started, and a newsletter.
http://www.ogametips.com/

OMarket
Assists with trades. Categorizes by language and universe.
http://www.omarket.org/

Wikipedia
Contains information on the various languages available as well as general information on the game and its gameplay. Also has screenshots.
http://en.wikipedia.org/wiki/Ogame

OGame.org
Answers questions and offers a weekly newsletter. [RSS]
http://www.ogametips.com/?rss=1