<script src="http://rndpic.appspot.com/user/your.username" type="text/javascript">
</script>
Replace "your.username" with your actual user name.The picture is clickable and the link takes you directly to the picture hosted on Picasa Web Albums.
Update: 9/14/2009
Due to a Bug in Google App Engine, contents of large albums (>~300 pictures) cannot be displayed properly at the moment.
Update: 3/25/2010
Thanks to partial responses the script now also supports showing albums with 400 or more photos.
Update: 1/16/2011
I finally uploaded the project to Google code. Check it out at https://github.com/pmoor/rndpic. In addition, I added the ability to specify custom sizes for the thumbnails as well as the option to turn off the link generation.
