We went with a 5v 3A regulator from CPT last year to power our Arduino and connected LED light strips.
This is the same company that makes the regulator for the wireless bridge.
http://www.current-logic.com/dcdc_co...cpt_fulree.php
- It's potted so no worries about shorts due to debris
- Screw terminals for easy mounting
- Cheap: You can find them on ebay for a few bucks
We didn't have any problems with it on/off season. This would certainly be overkill if all you needed to run was an arduino. If you need to drive other components as well off the supply though, it's a great option.