Copied this verbatim from the Nikon Cafe. That thread has gone on for years and is currently on it's ninth thread. Thought we should give it a try here and see if it lives.
"I saw this idea on another forum, and thought it was neat. The idea is to post an image of yours that has at least one thing in common (or similar) with the previous image posted, (subject, color, expression, mood, shape, angle, setting, anything at all) and briefly mention how its related (if you want to) so be creative!'