This is the best guide available anywhere regarding 12v systems. It has everything you need to know about batteries, inverters, converters, solar, control panels and much more. I used it myself to do my battery conversion and inverter install.
If you are needing parts for any of these systems...this is the best I have found on the internet.
http://www.windsun.com/
http://store.solar-electric.com/hardware---wire.html
Their pre-assembled battery and inverter cables and prices are a great deal and they ship fast.
This place has some of the best solar deals out there:
http://www.partsonsale.com/
enjoy!