I used the "2nd largest size" in all the brands as a good representation. These have different lengths listed by the ski manufacturer, but when they're on the rack they all are within about a centimeter of each other in actual tip-to-tail length.
The FIS allows skis down to 750 grams per pair, with no limitation on mass distribution. None of the ski makers is anywhere close to breaking that rule.
The measurements are in grams, and were made using an Acculab VI-4800 digital scale (with 0.1g resolution), using actual skis. Weights are for one ski, or one binding - not per pair. All of the skis listed are skate skis, but both skate and classic bindings are shown. In most cases I weighed 4 individual skis and averaged the results, rounding to the nearest gram. All the skis are 2010/2011 models.
You can see that the Atomic World Cup FeatherLight is about 10% lighter than nearest other offering. In fact the Fischer Hole Ski is 20% heavier than the Atomic. That's significant.
But it is worth taking a quick look at the "ski + binding" combinations, since that's what we actually ski on.
This is where things turn upside down. The lightest real world combinations is the Rossignol Xium WCS with the Xcelerator binding. The Atomic FeatherLight with the NNN R3 (screwed down binding) is only a few grams more. The Madshus Nanosonic with Xcelerator binding is close behind.
It's possible that you could skate on an Atomic FeatherLight with a ProPulse binding, and that would get you a total weight of under 600 grams for one ski+binding. But so far I haven't seen anyone use that setup. (Note: I called Salomon in October to ask if they've got firmer bumpers for the ProPulse, they weren't able to provide an answer - it was clearly, "I don't know...") With or without a firmer bumper, the ProPulse might be a possible skating option.
The "Pilot + Wedge" option with any ski makes a relatively heavy choice. And of course, the super-light Xcelerator binding will only fit on skis with an NIS plate.
Overall, you can get a ski+binding selection of a little over 1200 grams per pair if you're careful. While none of the brands are anywhere near the FIS limit, skis this year are quite a bit lighter than choices from just a few years ago. It does make a difference.