Google mobile team has made a mobile version of Picasa Web Albums for windows mobile users. To use the application on your windows mobile 6, just point your IE Mobile to http://picasaweb.google.com. You can also have the choice of storing your albums offline so that you can still view it when disconnected from the data connection.

According to the blog post,

Working with Windows Mobile also meant that we could add some cool features using the newly announced Google Gears for mobile, which gives web applications the ability to work even when there is no internet connection available. This means that you can view albums of your choice offline. Gears also lets you add a Picasa icon to your Program Files folder so you can have faster access to your favorite photos.

Source [googlemobile blog]