Some of you may have noticed some new features today.
First off, on the user profile pages you can add a photographer to your "Favorites" list.  Additionally, you can add them or a photo on the detail view of a POTD or World in Pictures Day entry.
To view your favorites, in the Account menu, there is a 
My Favorites option.  Here you can see your list of photographers and images -- as well as recent works (POTD, WPD and soon Thematics) from your favorite shutterbugs.
Another feature is when a comment is added to one of your photos, you will get an email notifying you of this with a link to come back and see the comment.  You can turn this on and off in your account settings.
More to come!