Use http://wap.google.com/ to view PM, especially to view raw chat messages.

To send chatter, use raw just_chat but not via google (google's WAP gateway simply throws away the contents of forms), though you'll have to log in first. I just use ?op=login;user=x;passwd=y (not via google) to get a cookie into my phone.

For reading your private messages (/msg), I currently don't have a good solution (but I don't read mine frequently so I'm not surprised).

                - tye