The Smith-Victor KF3U Thrifty Location 3-Light Kit with Umbrellas is one of the most economical flash kits available. The kit includes three FlashLite 45i AC Slave/Master units, swivel mounts, two umbrellas for softening the output, and three 8' light stands.
The built-in optical slave fires the second flash when it "sees" the light from the first unit.
The black-backed white umbrellas soften the output.