Here's v 0.96 of my fog script for Nightstalker. It's very picky and takes a lot of variables, but it allows you to create very specialized fog effects. You can turn it off when it's running by setting variable fogoff to 1.
Format: [object,amount,size,life,startalt,velocity,zvelocity,mercytimer] exec "drg_fog.sqs"
Object - Object that fog particles originate from.
Amount - # of fog particles produced per cycle.
Size - Size of each particles.
Life - How long each particle lasts before it's deleted.
Startalt - The height at which each particle starts.
Velocity - The xy velocity of each particle.
ZVelocity - The upward velocity of each particle.
Mercytimer - Time between creation cycles.
Example 1: [fog_mkr1,40,1,30,-1.5,1,0.15,2] exec "drg_fog.sqs"
Note: This creates fog that radiates up from the ground.
Example 2: [fog_mkr1,40,1,20,0.5,1,0,3] exec "drg_fog.sqs"
Note: This creates fog that glides along the ground.