The Insteon route is kind of expensive if you don't already own the Insteon hardware (normally just used for home automation lighting). You're also limited in how rapidly you can fire messages. The good news is you can program every device to respond simulatenously to group commands. Just as an example, I have group #31 set up to fade all my devices up or down at a ramp rate of 0.5 seconds, and group #180 is programmed to fade just 2 of my devices with a ramp rate of 8.5 seconds.
If you want to do lots of rapid fire effects, I'd recommend looking at the 16 channel box that
www.lightorama.com sells. It's over $400 but I believe you can do far better stuff with it, and includes the software. I'm thinking about maybe investing in one next year. Of course Insteon does have 1 advantage. There are no cords to route from my computer to outside. Insteon works off of power-line communications, meaning you can plug the devices into any outlet in your house and your computer will still be able to have full control over them.