The Envy 171 Series (you configure from a base minimum which must be used to support the 171 Series' extreme hardware and software) made by http://www.voodoopc.com (a different sort of HP division, to put it politely). Voodoo was bot by HP recently. You may wish to look at the HP-branded http://www.hp.com/blackbird as well ~ I don;'t know anyone personally who's trialled the Blackbird Series yet, but it specs very very hot. Tech & Customer support for this level of machine is on a whole different plabe as it should be for the price. I own a Voodoo desktop but recently configured one of their Envy 171 laptops for a friend who is a radical gamer and so far so good, as I'd expected.
There are loads of others ~ small niche companies making gaming machines ~ besides these HP gaming series. But many feel that Dell has degraded their XPS and Alienware series. I wouldn't know ~ I've only used a massive Alienware machine once and it rocked, but that was before the purchase of the firm by Dell. You may wish to check out their Area 51 Series if it still exists and you're a fan of Dell's.
Some advice. You'll have to choose between ab AMD and an Ibtel provessor. Who's in front goes in cycles. Intel's in front currently.You may have to choose between which dedicated Gtaphics Cards to use - ATI or NVIDIA. Go with NVIDIA's Go GeForce series (the word "Go" means laptop series in NVIDIA-speak lol). Memory ia cheap so do yourself a favor and get loads like 3 or 4 GB expandable upto 8 GB. If you choose 4 GB, you'll have to go with Ultimate to safely support the ware.
Here's a word of caution that's pretty serious ~ later this year, we expect NVIDIA to release its next more powerfrul card series (the 9000's for desktop and the Go 8000's for laptop) so you may want to wait. Even if the current pair of series suits your needs, it'll be pretty deeply discounted by then. Cooling systems ~ spend up foor quality unless you're ok with a fair amount of noise from your processors. Finally, we expect the RTM Vista SP1 soon and Lord knows what impact that'll have on all of this high-end gaming gear. On that note, please bear in mind the essential difference between desktops and laptops where gaming gear is converned. It's fairly easy to upgrade parts on a large Tower, but not so on a small Laptop.