This information is from Strobist which is an excellent site I highly recommend.

Sometimes you need a little extra power when there is nary a monobloc in sight. For one quick solution, follow the bouncing ball bungee as Paul Morton and Darren Stevenson show you how to mount three SB-800′s into a softbox.

This is 3x better than the cheater, which will mount suspend a single SB in a speedring with the CLS window showing, a la the Strobies XS setup.

But remember, three strobes only buys you a stop and a half more power. The first additional flash doubles your power, which adds one more stop. The second one goes halfway to doubling it again, adding another half stop. But put them on 24mm zoom for good coverage and lose the internal baffle and you can definitely get up to full sun-balancing levels at close range.