Borrowed from http://www.folj.com/puzzles/
Four tasmanian camels traveling on a very narrow ledge encounter four tasmanian camels coming the other way.
Tasmanian camels never go backwards, especially when on a precarious ledge. The camels will climb over each other, but only if there is a camel sized space on the other side.
The camels didn't see each other until there was only exactly one camel's width between the two groups.
How can all camels pass, allowing both groups to go on their way, without any camel reversing?
Hint: to help visualize, use paper clips or coins.