As the album owner, you decide exactly who has access to your album. In addition to the different levels of album visibility, Picasa Web Albums lets you keep track of the users you've shared an album with. Adding people to the "Shared with" list has the following benefits:
- Easy access. The people on this list are the only ones that can see albums set to the "Sign-in required to view" access level. Plus, everyone on this list can see the album on your public gallery regardless of changes you make to album visibility.
- Email notification. Everyone you invite using the Share button is added to the list and will receive an email invitation to view your photos. They also get notified when new photos are uploaded to the album in the future.
- Collaboration. You can choose to let people on the list add photos to your album.
Sharing - Granting album access
Use the Share button in Picasa or Picasa Web Albums to add people to the "Shared with" list and to send them an email invitation to view the album. Follow these steps:
- Click the Share button in the Picasa software or Picasa Web Albums.
Picasa Picasa Web Albums 
- Add your friends and family. You can add both individual users and entire Google contact groups to the "Shared with" list.
- Share with individual people
Add the email addresses of the people you'd like to share with in the 'To:' field of the sharing dialog. Sending email invitations to group aliases won't add each member of the group to the "Shared with" list. Read on for more information on sharing with Google contact groups. - Share with Google contact groups
You can also share directly with your Google Account contact groups -- collections of Friends, Family, Coworkers, etc -- rather than with every individual person. This gives access to all members of that group. Don't have any contact groups? Create them in Gmail with a few clicks.
Picasa : In the sharing dialog, click the 
button to add entire the contact group.Picasa Web Albums: In the sharing dialog, check the box next to the contact group. 
- Share with individual people
- Click Send.
button to add entire the contact group.
The Share button is the most direct way to share your photos, but there are several other convenient ways to invite your contact groups to view your photos. In Picasa Web Albums, you can share with contact groups when creating a new album or editing an existing album. In the Picasa software, you can share with contact groups when uploading or importing new photos. When sharing in this way, members of the group won't get an email invitation; however, they'll be notified if they're opted into the Picasa Web Albums email digest.
Managing album access
You can remove an individual or a Google contact group from the "Shared with" list at any time. Just click the 
icon next to the email address or contact group to remove album access. Click Edit next to the contact group to add and remove users from the group and therefore the 'Shared with' list. Keep in mind that changes made to Google contact groups will affect all products that use your Google contact groups.
