Waves has 2 versions of the phase alignment tool plugin. the more expensive one looks like a very in depth tool and I would love to have it, but I'm not going to pay for it. the cheaper version doesn't have all of the comparison features in it.
Voxengo has a phase alignment plugin, but I've not used it either. Just thought I'd mention it. I had looked for these plugins before and never did buy one. I still want one, I just can't justify the cost at this point.
http://www.voxengo.com/product/pha979/ I have ONE song that the phase was driving me nuts on and I still can't seem to get it right, but I don't want to spend $70 or more on a plugin for one song.