ALL the above is good advice, maybe I can help keep it uncomplicated but still useful to your needs.
A few things I feel are minimum to have a useful Laptop for todays aps., be it new are old, and useful in a caching environment:
AMD or INTEL processor (laptops get hot so donít spare on the chip), other things will help cool but start here. *this is just a personal opinion*
An AC/ciglighter adapter (batteries are better now but Iím sure you will not think your laptop is as cacher friendly when unplugged)
A CD-ROM of any speed (almost all programs worth having are too big for any other device) very old ones didn't have them. R/RW/DVD etc are more useful.
At least 2 usb ports, you can hook lots of stuff to them and do sooo few things without them and I feel they are a must if you plan to cache with your laptop, 4 ports are better.
A PCMCIA slot (for all those things like WiFi). Better to have a cheap card in a good one than an expensive card in a cheap one.
A Mini USB (*optical only*) mouse. You are not going to like the things that happen if you are trying to use the touch-pad while bouncing around in your cachemobile.
A serial port or a serial adapter. Some cords use serial ports
USB cords for your GPS, PDA, Digital Camera, etc. *A cheaper way is to order a kit and make them yourself or get them out of Canada.* (your mileage may vary)
A cheap USB to RJ45 network/ethernet adapter for the Hotel/Motel that is still hardwired plus other uses.
A carry case with lots of pockets and a shoulder strap.
There are many more things you may find useful later (plus it is after midnight so I'm typing and thinking with one eye shut ) but I feel these are so basic and if there is anything I would drop from this list it would be the PCMCIA slot, but before I would drop the CD-ROM I would opt for a palm or iPaq, etc.
Also If you find your laptop it is actually useful it will lead a ruff life so getting a refurb with full warranty or an old used one and spending the extra cash for way-cool programs or even a GPS (they are small like chips) for your PC would be a good choice.
**The mileage of others may vary from mine somewhat but I bet it wont
be by much on the basic stuff.**
Live a good, honorable life. Then when you get older and think back, you'll enjoy it a second time.