After taking a batch of photos at the office today, I came to upload them to Flickr, and noticed that a new feature has been added. I say "new", it was a month ago, I don't take all that many photos.
Collections allow a bit more organisation of images, and allow sets of photos to be grouped. Two obvious groups suggested themselves.
These collections are unlikely to grow much since I'm leaving Sophos and Swindon later this month and going to pastures new. No doubt other collections will suggest themselves though.