[Joe Ross]

If you're looking at new laptops, the Dell 600m has a serial port, and is light (less then 5 lbs), fast (centrino), and cheap (< $1000 for barebones).

The IBM X and T series are great, but at least the newer ones don't have serial ports (I own a T 40).

As for USB-Serial adapters, some work great, some work poorly, and some don't work at all. I have an FTDI adapter that works perfectly (once I got the drivers installed properly). Joe Johnson and others recommend one by BAFO. Don't get one that is designed for PDAs, as they typically do not have all the handshaking lines that the IFI loader requires.