I run a couple of captioning sites where you can make fun of photos.

Inventing Situations gives you a new picture every half minute or so and displays your captions with everybody else's as soon as you submit - creating a friendly chat room sort of scene.

Wasting Precious Time lets you write stories around a series of images.

Some of the earlier pictures in my stream come form the same place as the pictures on those sites: archive.org and an assortment of similar sources that end up at my captioning sites. Plus, most of these images are from the public domain and labeled as such!