NovoTalk

a free Google Chat client

Features:
Text messages
Avatars
Finger Touch/Scroll Friend List
Marquee for long status messages
New email notification
Tab based Chatting
Notification on new Message (sound + vibrate)
Detect Invisible Users
Friend list sorted just like Windows client (Gtalk) on basis of availabilty and name.
Cool GUI

Notes
NovoTalk is written in C#, so .Net CF 3.5 will be required.
Might not work properly on smartphones.
Tested by on WM 5,6,6.1 and on HTC Touch with WM 6.5

NovoTalk