The Vikings are fun, IMO, because of the Berserker. Rather weak on defence (2 defence for their 70-shield cost), but 6 attack is the strongest until the much-latest Cavalry (Berserkers are available upon the invention of Invention), and isn't surpassed until Tanks. And all the better, they're amphibious. The only amphibious unit until Marines. So you can really go a different direction than with most civs - coastal raiding in the Middle Ages. And even on land, Berserkers can be a force to be reckoned with if they have a few pikemen along for cheap defence.
The Vikings are also Militaristic, and more important, Seafaring - the perfect complement for Berserkers. Nothing like having nearly-unstoppable Berserkers who can attack from the sea and can get there extra-quick!
Zardnaar, there are still people playing Civ3. Whether it's worth you writing more strategy guides for, you'll have to decide.