Organizing with name tags
Once you've added name tags, your photos will be organized by what frequently matters the most -- who's in them.
Picasa uses the People collection to group the name tags you add to your photos. Each person has their own album which contains all of the photos that you've tagged them in - finding 'all pictures of dad' is now much easier. It's also possible to find all photos containing multiple people. When viewing a person's album, open up the People tab (on the right) and click on another person's face to see all photos of those two people together.
Picasa Web Albums
In Picasa Web Albums, your name-tagged photos will be grouped on the 'People in my photos' page according to the people you've identified in the photos. On the My Photos page, click the View All link next to 'People in my photos.' Then click View all for a particular person to see all photos that contain their name tag. Click the Share button to share a customized album containing the public photos of the selected person.