My wife has used the standard Blogger photo upload functionality in her blog, so all the photos ended up on Picasa. Today she ran out of space. We noticed however, that in Picassa some of the pictures are duplicated (triplicated, etc.) How can I figure out which ones? We use Picasa only for Blogger, so an automated script to detect all the photos that are unused in Blogger would be ideal.

Even checking the photos one-by-one is tricky - the link in Blogger is completely different from the link in Picasa. How can we determine manually which ones match?