If you’ve been active in IPv6 area for some time now, you have probably found already the very good GetIPv6 Wiki Page
What you probably haven’t seen yet (at least I haven’t) is a comprehensive list of mobile handsets and USB dongles that have been tested and are known to support IPv6.
I decided to compile such a list. It strictly includes those devices that are commercially available, have been tested and are known to work. IPv6 support is described for both GPRS/UMTS and WiFi interfaces. All the data provided is to best of my knowledge, but can change in time. I would advice you recheck yourself when you get around the gear.
The spreadsheet with the list of mobile devices supporting IPv6 can be found here.
I would appreciate contributions to make the list as complete and correct as possible.