Found a great post and bit of software at the following address:

http://dalelane.co.uk/blog/?p=244

Download the CAB to your mobile device (Windows Mobile with touchscreen). Run the application from there (I installed to the device as read installing to the card may have an issue). Go to Start > Settings > Today and click on the "Items" tab. Ensure that "bLADE TwitToday" is ticked. Highlight it, and click "Options" to enter your Twitter username and password.

From your Today screen you should then be able to post directly to your Twitter profile. You can also click on the icon to load the mobile twitter feed.