A friend of mine replaces his desktop with an Alienware Area51. 3.2ghz beefed up mofo.
I plan on replacing my desktop by the end of the year with a Dell Inspiron 8600. That's a bad ass computer with the pentium M so it lasts for a long time. And you can game on it if you want to (light gaming).
My only problem is storage. I'm not sure if I should keep a desktop, or just get a USB external hard drive holder and slap in a 250gb drive. This might be the best answer.
For more info about laptops and recommendations you could always check this place out:
http://www.notebookforums.com/
Dell often has 20% off coupons too. I just priced an 8600 at $2800 and it came to $2100 after the 20% discount and their other special offers like free shipping. I almost ordered it but decided to wait.