I got a invitation mail of my freind for photosharing album Snapphish. But I already had acc. in Flickr. Now there are such number of photosharing sites available on net. Its being really great to store your moments in web album.
So advantages of them like
1. Viewing slideshows.
2. Easily updatable labels and title.
3. Sharing with friends.
4. Update your profile, hobbies.
5. Save their contacts.
5. Blogging with photo acc.
One most widely used photosite that i use is http://flickr.com