Michael, I think there are a lot of good suggestion so far, but you might ask yourself whether or not you actually need a full laptop in the field. You can do a lot with a PDA, especially with a database program and some creativity. They're lightweight and have good battery life (>10 hrs with extended batteries). We use ruggedized and unruggedized (in a waterproof pouch)PDAs in the rainy PNW with good results. You might be able to leave the laptop in the truck and work with a PDA.
Cheers, Peter
