This "Nuclear Weapon Design 101" article is really nifty as long as you don't think too much about it. Especially startling is it's matter-of-fact discussions of countries the mainstream media just think might have or have had (or have tried to build) nukes (North Korea, South Africa, Iraq). Also provides confirmation of something that's been hinted at in several books and documentaries I've read/seen over the years... there is essentially no upper limit to the destructive power of an H-bomb. Once a country figures out how to make one (the article implies only a few have, the usual suspects), a planet buster is as possible as a bunker buster.
Which is why I personally think the underground facilities Iran is beavering away at have a clock ticking on them somewhere. I'm hoping it's in a B-2 hangar, but at this point I'd be nearly as happy if it were an Israeli squadron of F-15s. At least they don't even pretend to care if they piss off Arabs.
Oh come on. Do you really think it's an accident we've been working on deep-penetration precision weapons for the past ten years? What, you think we want to just root out guys in caves with these things?