I have the Dell 600M and I am very happy about it. It is Centrino with 802.11b. But you can buy the 802.11g card online (not from Dell of course) and swap it yourself.... much much much cheaper that way.
The 600M is thin and lightweight... under 5lb. It also come with the CDRW+DVD Rom combo drive, free of charge. I added a few upgrades.... Win XP Pro (I hate Home edition), SXGA, bigger hard-drive. With all of that, I paid just under $1400. The best value for the money!!!!