I have a nagging fear that researching the answer to this question from my home computer is gonna get me Ashcrofted to some secret military prison on suspicion of being a terrorist. (Now that I think about it, if they do put me in a cell next to John "American Taliban" Walker, Zacarias "20th Hijacker" Moussaoui or Jose "Dirty Bomber" Padilla, I could probably write one hell of a Don't Panic! column when I get out.)
The unfortunate answer to the question is that it's very easy to find bomb-making recipes on the Internet. A few years ago, bomb-making instructions -- along with porn and chat rooms -- were the subject of countless TV news stories and a Congressional investigation about how dangerous the Internet is. The danger is real, even though the actual threat was played up by grandstanding politicians and TV producers looking to boost ratings by running "Is your teen building bombs?" stories alongside the usual "Is your teen fellating other teens at parties?" stories.
I found my first bomb recipe in about a minute by using a regular search engine. It's easier to find this sort of stuff than it is to find bootleg recordings of my favorite musicians -- which is one of my other favorite illegal online hobbies. And no, I'm not gonna tell you the recipes or where I found them.
One of listings that I will talk about is an online transcription of a book called The Anarchist Cookbook. It's been in the news before and is available at major bookstores, so I don't think I'm endangering anyone by mentioning it here. It's clearly geared to trouble-making teenage boys. One of its chapter's even starts, "One of my favorites for getting out of a class or two is to call in a bomb threat." In fact, there are just as many tips for getting high in The Anarchist Cookbook as there are for making bombs. My hope is that chapter titled "Growing Marijuana" is so informative that readers will be too stoned to move on to the bomb-making chapters.
The recipes listed in The Anarchist Cookbook use ingredients that are mostly available at grocery and hardware stores. And since I have no intention of testing them myself, I don't know how accurate the instructions are. Several of the customer reviews for the book on Amazon.com state that the recipes are inaccurate, and that following them is more likely to get a would-be bomb maker blown-up than it is to produce a working explosive device. Darwinism at work, I suppose.
The most disturbing thing I found was an online discount pharmacy offering "Ammonium Nitrate shipped discretely." Ammonium nitrate is the fertilizer used in the Oklahoma City bombing. It's perfectly legal, though law enforcement agencies are always looking out for the purchase of large quantities by anyone with no links to agriculture. That someone is offering to ship some to me "discretely" is a bit worrisome.