I just stumbled upon this site (from http://blogs.technet.com/jkruse/archive/2009/05/05/download-communicator-mobile-clients-directly-to-your-cell-phone.aspx) that you can use to download Communicator Mobile directly to your phone (Windows mobile or Java client)
Try it here: www.getcomo.com
Rasmus
Did not work on HTC HD2, did the direct install and works like a charm