From my personal experience, I'd like to recommend the Systemax Ruggedized Laptop computer. It's available from tigerdirect.com. I can't actually say how rugged the unit is or what the difference is between it and a non-ruggedized computer is but I've had mine for about 2 years, on and off my boat and traveling by train, plane and bus. It's never failed or even slowed down. I think it's one of the few laptops that can still be ordered with Windows XP Pro and comes with a serial port - great for using Sail Mail or Win Link. The built-in wireless will pick up a signal from inside my cabin without an external antenna. The unit is a little on the heavy side but perhaps that's because it's ruggedized - who knows? Heck, maybe it's the same computer as the non-ruggedized - I don't know. Regardless, it does have the features (and, so far, the reliability) that I need. By the way, I don't work for either Systemax or tigerdirect.com. Good luck.
We have had great success with the Panasonic Toughbook, we also have one of their tablets, which takes over the host PC. both are built to mil specs and can take a soaking, etc. we have mor on this on coastalboating.net