For a generic laptop you are looking at a (A) basic, (B) desktop-quality, or (C) high-end. Basic laptops will go for around $500, they will do word processing, internet, etc, but will snag once in a while on big multimedia. Desktop-quality are around $1,000, these are excellent desktop substitutes. Anything above $1,500 is Luxury/Professional (high-end).
The two brands I've had the most success with lately are Dell and HP. Historically Toshiba has been a dog that overheats and Lenovo is a China-fied IBM thinkpad (not sure what that means for their quality these days).
*** Good basic laptops:
Dell Inspiron 15:
http://www.dell.com/us/en/home/laptops_great_deals/fs.aspx?refid=laptops_great_deals&s=dhs&cs=19
HP Pavilion dv6z:
http://www.shopping.hp.com/webapp/shopping/computer_can_series.do?storeName=computer_store&category=notebooks&a1=Category&v1=Everyday+computing&series_name=dv6z_series&jumpid=in_R329_prodexp/hhoslp/psg/notebooks/Everyday_computing/dv6z_series
*** Good desktop-replacements:
HP Pavilion dv6t:
http://www.shopping.hp.com/webapp/shopping/computer_can_series.do?storeName=computer_store&category=notebooks&a1=Category&v1=High+performance&series_name=dv6tqe_series&jumpid=in_R329_prodexp/hhoslp/psg/notebooks/High_performance/dv6tqe_series
Dell Latitude 6500:
http://www.dell.com/us/en/business/notebooks/laptop_latitude_e6500/pd.aspx?refid=laptop_latitude_e6500&s=bsd&cs=04
If you have some special uses, like gaming, hard-core video editing, etc, you probably want to look at something like Alienware. If you tend to drop your laptop out of the window, you may want to look at a Toshiba toughbook.
"Techie" things to know:
1. Not getting a separate video card will slow down your computer overall. Unless you're getting "basic", I recommend to always make sure you have a dedicated video card in your laptop.
2. One of the slowest parts on laptops is the hard drive. If at all possible, make sure your HD is 7200RPM (vs 5400RPM) or, if available and affordable, get a flash-drive (like Intel X25-M), which is sturdier and in many cases faster than triditional plate spinners.
3. RAM is your best friend in laptop performance. 4GB of ram is a good way to go.
4. Intel, unfortunately, trumps AMD chips in mobile options and performance these days (Dec, 2009). I would avoid obscure chip names and try to make sure your laptop has a "Core 2 Duo" of some flavor.
5. Screen size is directly proportional to bulkiness. If you will be carrying the laptop around every day, you are probably ok with 14-15". If the laptop is mostly a stay-at-home, you can go for the larger screens.