Flickr is groups. We all post to groups. Most of us start and run groups. Some groups are obvious: nikon, grand canyon, black and white portraits, sunsets.
Some groups are weird. Really weird. Hydrants-a-Gogo, for instance, is a group with 1,277 images of, yes, fire hydrants. Matchbooks & Collectable Matchbooks is what it says. Also see Ants, Trash, Men’s Shoes, Sock Heaven, Toes in the Tub, and Nail Art. Then there’s One Bottle, Three, Four-on-a-Couch, and The Five Dollar Comparison (a group of photographs of stuff that cost five bucks!)
And finally, of course, this is the aptly named group Weird Shit.