I've had a Dell Inspiron 4000 and I'm currently running an HP Pavilion ze4805us. I can tell you now that you won't get a laptop that will not be outdated in a year or two, especially if you're only paying $500 to 700. when I bought my Dell 5 years ago, it was outdated in 3 months because they started releasing Dell laptops with a 1GHz processor. Having a laptop is very convenient, but the staying power is not very long. Just keep that in mind.
I'm not a huge Dell fan anymore. My Inspiron 4000 started 'highlighting' blue colors after about 6 months because I believe the ribbon cable went bad or was poorly connected. Fortunately, it had a flimsy screen that could be used to adjust the problem (by pressing on the back). I was going to send it back to Dell at some point, but I had a presentation to do, and just neglected to do it. The Dell Inspiron 4000 was a somewhat wimpy setup, although it was pretty sleek.
My wife has an Inspiron 8000. Not too bad. Both of these laptops cost around $1500 when they were new.
My recent purchase is my hp. I'm happier about it, but there were some software issues with the bios that prevented me from running a PCMCIA card for USB 2.0 and firewire transfers. Once I figured that out I was happier. This thing is built like a tank, but isn't too heavy. Cost was $1000 when all was said and done.
A number of people in my working group have IBMs. They're happy about them, but they're also upwards of 2k.
If you can find a good Dell or hp for cheap, get them. If you want to shell out the extra cash, get an IBM. Regardless, most laptops will be out of date within 6 months or, if you're lucky, a year. Be prepared to live with it. If you can wait, development of Blu-Ray or HD-DVD is getting close to getting out on the market and dual processor CPUs from both AMD and Intel should be hitting the market late 2006. This will boost processing power and the amount of data to store on a DVD. However, as with any new tech, it will be expensive at first, so you're probably better off getting a good laptop now.
Most laptops come with internal wireless network cards now, but make sure that the one you choose has one. It's also important to list what you want to use the laptop for in the end, so you can buy one for your specs. If you're going to just surf internet, check bball, word processing, low end should be fine. If you plan on getting into video editing, make sure you have a fast hard disk, and firewire/usb 2.0 connections.