Picasa resizes images before uploading which is great as it prevents people trying to upload those 3mb images straight from their camera. However by default it only sends images to Picasa web albums or Blogger.
However! Google have released an API to do this and also create a button in the Picasa desktop application. See:
http://code.google.com/apis/picasa/docs/web_uploader.html
Unfortunately it's beyond me. Perhaps someone could create such a thing for WP?
There's a module for 'Gallery' that someone's written which might be a good php starting point for someone: