Tribal Trouble 2
"Tribal Trouble 2 is a fast-paced realtime strategy game set in the wacky Viking age where pillaging and plundering were everyone's favorite pastimes.
Create your own Viking chieftain (or chieftess), sail on quests to foreign places, challenge other online players to battle and then go spend your loot on more Viking gear!" - Website Info
Windows 2000/XP/Vista, Mac OS X 10.4+ or an updated Linux distribution.
Internet Connection and Browser : Firefox 2+ or Internet Explorer 7. Other browsers may or may not work. Internet Explorer 6 most certainly won't.
Sun Java plugin: If you don't have this, your browser will automatically prompt you to install it. Otherwise, it is available for download at java.com. Version 1.5 or newer is required.
Video card with full OpenGL 1.2 support