Like Jeremy I love TinyTwitter and they have just released a new version. If you already have it on your Windows Mobile, do a version check and you’ll be prompted to download the new release. It includes some cool new features

• Picture uploads: append a picture to any tweet and it gets posted to TwitPic with no additional work needed by you. Magic! 
• Geolocation: if you have a GPS you can tell everyone where you are. It takes the boring latitude and longitude numbers your GPS returns and can do a reverse address lookup to tell you where you are near – plus it posts it to your timeline along with a Live Maps link so people can see where you are on a map as well.