I won't go into specifics but if you are going to do photoshop on it, this is what I would recommend as minimum.
17" High Res Screen (1920 at least)
One of Intel's i series processors.
64-Bit Windows 7
64-Bit PSCS5
4 GB memory barest minimum. More is better that's why 64-bit W7 is needed.
320 GB min HD. 500 GB would be better.
High-end Video Card
Since you will probably be using external HD's I suggest the fastest ports your can get like SATA, USB 3, Firewire.
I have no idea what is available in high end laptops since I do all my PS work on a desktop and only use laptops for editing and lightweight PS'ing.
So just throwing some thoughts out there. Perhaps someone else has a more specific recommendation. But if I was looking at specs, that is where I would start.
You need to give us more info. My idea of a laptop is for travel, and I generally want to travel with a light laptop (because the photo gear usually weighs a lot). So I look for a smaller, lighter laptop but with large hard drive (500 GB or more). Note I just bought a 1.5 terabyte usb 3 drive in the small 2.5-inch form factor. Now I need a laptop with usb 3!
My last specs were about 13 to 14-inch screen, 600+ GB, 6 GBytes ram, under 4 pounds. Yes, I found it. Maybe more choices today. Now I would add LED backlit display.
I would argue that for photographic work/editing the screen is the most important component of the laptop (and desktop). The TN and VA/MVA types are considered to be below, not as good, as the others for color accuracy, contrast, and viewing angle. I would for sure know what technology the laptop screen is and preferably also actually see it.
I am with Roger on that one- the smaller the better for a laptop, although I understand the netbooks are too small and underpowered to run full versions of Photoshop. Are you a Mac or PC user? If the former, the choice is a lot simpler.
I just went through the debate on the MacBook Air versus the MacBook Pro. While the screen at 13" is smaller than the 15" I just am retiring, the AIR SCREAMS!!! I run photoshop with large RAW images from my Canon 7D and have no challenges. The Pro may be faster still, but there is a point of diminishing returns for me. Plus the fully loaded Air was $400 cheaper.
I'll also say that I lost about 4 pounds in travel weight with back up batteries and chargers.