binyo66 said:
I should have implemented in my last game (where I lost suntzu by 8 turns

)!! I knew I read it long time ago, somehow I forgot about it.
Since you can't mobilize until you reach nationalism I don't think it would have helped with Sun Tzu

.
The article Padma linked to is excellent. Here's a brief summary of the main points of mobilization:
1) You can mobilize at any point after researching nationalism, but you can't demobilize until you have signed at least one peace treaty.
2) When you mobilize, every tile that already produces at least 1 shield produces another, so long as you are producing military* (explanation below). So it is a bit like having a Golden Age, except that it is only for shields, not gold.
3) The extra shields only apply to "military" production. The definition Civ 3 implements of military production is a bit wierd. Most units count. Military buildings (eg barracks) count (I think). Strangely, artillery does NOT count, nor do aircraft, yet nukes DO count.
4) While in mobilization you cannot build any "peaceful" buildings. This means anything except barracks, walls, harbours, airports and wonders. For wonders you do NOT get the extra shields (I think). You can build all units, but you will only get the shield boost for military units, eg, you can build settlers but you won't get the extra shields from mobilization for settlers.
5) EDIT: forgot to add the half-culture! When mobilized, culture buildings only produce half normal culture, eg a temple usually produces 2cpt, in mobilization it will only produce 1cpt. So if you're playing a game where fast culture is part of your plan, try to avoid mobilization.