Any tips for blocking an address range for outgoing packets? Anyone used ipfw or pfctl to block an IP address range for outgoing packets?

I would like to temporarily block Apple's IP address range 17.*.*.* to find everything that's phoning home phoning home.  Anyone know if Apple owns any other IP address ranges?
I highly recommend Little Snitch. Although it doesn't do anything you couldn't do with free tools, it makes monitoring, configuring, and blocking your system's outgoing traffic on a per-application basis ridiculously easy.

I'm a programmer, and one of those guys who always has a Terminal window open, and yet I still prefer using Little Snitch for this task.

It's not free, but it is cheap.  And the free trial is fully functional - the only caveat is you have to manually restart it every 3 hours.

That would probably be all you need to open all your Apple-branded apps and verify whether or not they're phoning the mothership.

And if they are phoning any address outside the 17.x.x.x range, you'd learn that really quick.