AI for Game Developers has a chapter on flocking, and I thought I’d try it:

Click to play! It’s not polished, but it lets you explore different flocking behaviors. Here’s what the controls do:

• count The number of “birds” in the simulation.
• alignmentRadius Birds rotate to match the direction of their neighbors. This parameter changes how far away they can “see”. Larger values tend to align the entire flock; small values let the flock break apart.
• separationRadius Birds try to avoid colliding with nearby walls and other birds. They will turn and simultaneously hit the brakes. This number controls their stopping distance.
• peripheralVision Birds have a blind spot behind them. When this slider is maximized, the birds will have no blind spot, and will see 360 degrees.
• turnSpeed The speed at which birds turn.
• brakePedal Birds will slow down to avoid colliding. When this slider is minimized, the birds will never use their brakes.
• travelSpeed The top speed of the birds.
• Scatter and Randomize: Try them and see…

If you want access to the code, the SubVersion repository is open: http://dev.zacharcher.com/svn/flocking_test/