Yahoo! has released their Yahoo! Go application which was earlier only for Symbian S60 for Windows Mobile based 2003 and 5.0 Pocket PCs and smartphones with the following features:

Contacts ? Stored phone numbers are automatically synched
Photos ? Take a picture and it’s stored online
Mail ? Get notified when new email arrives

Messenger ? Record voice instant messages is currently not available for Windows mobile devices.

You can install the app via Activesync or Over the Air.