Feature 1 - Face recognition: Though this feature was released on 9/02/2008, I noticed it only recently. Worth trying it!

How to use it?

• Log into Picasa Web Album, go to Settings (top right corner) page, you will be able to find a section ‘Name Tags’, and right below it there should be a button ‘Turn name tags ON’, click it. After few seconds Picasa will start auto face recognition, you should be able to see the progress on the right side of your picasa home page.
• Once it is done, you can click a photo (your photo or any of your friend’s photos) from any of your albums, picasa will show a rectangle around the face of the person in the photo, you can add a name tag.
• Now, go to ‘People’ tab and add more name tags. See below video for more info.
  
  

Feature 2 – Email Upload: You can upload photos to your album by forwarding emails addressed to your picasa emailid. You will be able to add a picasa emailid on Settings page, under ‘Upload Photos by Email’ section.

Feature 3 – Meta tag info: I think this was there since picasa was introduced, but I came to know this only recently from one of my friends. I added few web albums and sent the links to my friend; he was able to tell the camera that was used to take the photographs, apertures, focal length etc. Picasa reads the meta tag info of the photo and displays on the right hand side of the photo under ‘Photo Information’, click link more info.