I lived in the Philippines for nearly two years and used only the disposable silica gel around my computer, camera, and electronic components the entire time. They would collect about 10oz of water ever month (inside an air-conditioned house!) If you're planning on being in a VERY humid or rainy environment like the Amazon, I'd suggest saving your money for Pelican cases instead. You _can_ buy 'rechargeable' silica gel (maybe at a pool supply place?) that changes color. Then you can pop it in an oven and bake it back to dry.
Otherwise I’d place all my camera equipment in a nice air-tight case and toss a couple of silica gel packets in on top of it (I'd steal them form my wife's shoe boxes personally). Hope this helps.
A few links for silica for sale on the web:
http://www.jakesmp.net/CSD_Silica_Gel/CSD_Silica_001_M.html
http://www.drierite.com/default.cfm
I can’t even begin to help with batteries/recharging systems because I’m in the middle of deciding on solar :sunflower panels myself. That Brunton that Scott posted is pretty cool because it (supposedly) generates 900mA. You can get lower current ones for less. With that flexible one you could use little suction cups in a back/side window of say a 4runner
and charge batteries all day long while driving OR parked.
I like this universal (1.2V-14.4V batteries / 100V-240V AC OR 12V DC input) battery charger, and plan on ordering one very soon:
http://www.thomas-distributing.com/mh-c777plus.htm
And it should connect nicely to a panel once I find a nice, tough one. Uni-solar makes them for the military.