A couple of days ago, I included this story in the newsposts:

US fired phosphorus in Iraq, tv reports

I don't have the requisite military knowledge to make a technical response to the allegations, so I'll defer to someone who does.

Here's a snippet of NOTR's (ROFASix) take on the situation:

Willy Pete is stuff every soldier knows well. It comes in grenades, artillery, bombs, and is used in smoke munitions. Is it a "chemical weapon"? Only if you can try and make the stretch that white phosphorus is a chemical therefore it is a chemical weapon. Of course that logic would also lead you to conclude that since gunpowder is a chemical, every IED or bullet is also a chemical weapon. But the real problem with the charge is that magnesium, not Willy Pete is what is used in illumination rounds.

I also am somewhat skeptical about this claim because last year's actions in Fallujah were widely covered by all sorts of media, and I have a hard time believing they'd wait a year to put out a negative story about the U.S. military.

Go check out Documentary alleges US used chemical warfare in Iraq at ROFASix