I use Xten free world dail up. Great free program. The x3i mic is so sensitive/responsive that i can set my x3i on a desk 2ft away from mouth and the person on the other line will easily pick up my voice. My PC mic you have to be 2 inches away with this program so it is a big difference.
This program doesn't run through AIM though but there is a PC version of this software so if he is on PC and you are on X3i you can still communicate :)
Looking on their
siteI can't find the Pocket PC version of it but it seems to be somewhere since people are talking about it in the forums there.