Flickr has added people-tagging. Tagging photos with little notes has been a feature of the service for a while, but the new feature allows you to highlight faces and link to Flickr users in your picture, similar to tagging in Facebook.
To get started, simply double-click on or draw a box around the person you want to tag. Select whether you're adding a note or a person, and type the person's name. Flickr searches your contacts first, then every user of the site. Non-users can be emailed to ask if they want to be tagged.
When someone tags you, you get a message in Flickr and an email. The photo shows up in your activity stream, and you can see all the pictures graced by your face in your profile, similar to Facebook.
Privacy settings allow you to specify who can tag you: friends or family or a combination of the two, contacts, all users, or no-one but you. There's even a big red button to kill all your tags.
If you already have a photostream full of phizzogs, a batch face-tagging tool is available. There goes our weekend.