the most recent batch of hp laptops we rolled out at corporate all had resolutions of 1280x800 as default, 14" widescreen displays, they also support 1024x768 but look really good at 1280x800. The previous flock of dell corporate laptops were running widescreen displays also but a funky 1440x900 or some odd resolution, looked a bit wonky but worked.
1280x800 and 1024x768 would probably be the default setups for laptops,
desktops though with their infinite display possibilities due to wicked huge monitors can go anywhere, it's pretty hard to say what the common sizes would be for those. I know people who have purchased new flat screen displays 2-3 months after purchasing their previous flat screen display just to get a bigger size.
People always wanting something bigger, probably trying to compensate for something else