Dell Latitude X1, but they don't sell it anymore. It is actually a Samsung notebook, and it's successor apparently is the Q40 (http://www.dynamism.com/q40/main.shtml).

Now I love this nb, actually it is the only acceptable notebook that I know of:

#1 FANLESS - no annoying noises whatsoever!!! #2 really, really lightweight, less than 2,2lb if you remove the battery (2,4lb with battery) - external dvd drive, though

I have tried a MacBook, but it was too noisy for my taste. Hoping that Apple will produce a fanless subnotebook one day...