Cyanide gas weapon, one example of instructions found onlineFound lurking in a 'throw-away' geocities account used for serving content linked to from various Arabic-language jihadist forums. Here's one slighly censored illustration:
The concept is pretty straight forward: a can with holes, a couple of chemicals in vials, each of which are fairly toxic in their own right, and all of which, if combined correctly, will result in the release of cyanide gas.
This is pretty typical of the stuff we're seeing these days. A rich mix of promises of some "blessed event" involving the death of many Americans, combined with howto instructions so that the new recruits can learn the tools and tricks of the trade in an environment where travel and communications are a little more difficult than they used to be.
I listen with a large grain of salt. Of course, MY knowledge of the Muslim world is confined to what I have learned since 9/11, so I am not really a good judge.