Does anyone know of one? If so, what is it?

While shopping for a laptop or any pc , I've discovered it really helps to go into a retail store and run the recent ubuntu 8.10 live. Ubuntu has some "propriety hardware detection" software, but I've discovered much to my dissapointment that live ubuntu doesn't come with a program that shows specs as specific as Windows xp "device manager"

Sisoft Sandra for Windows was always a classic.

So is this:

http://www.passmark.com/products/index.htm

Is there any distro with something that has a good offline hardware recognition software with good diagnostics features so that I can boot it and see what it does?

Not sure, but take a look at ubcd, it has a lot of good info and diagnostics programs packed on it. I always keep one around:
http://ubcd.sourceforge.net/
(scroll down)

the mandriva dvd has nifty testing