Along the lines of Locale, I've been running this oddball thing called "Auto Wifi Enabler" which keeps track of your coarse location (network-based, not GPS-based) when you're using Wifi. It then disables the Wifi when you're outside of those areas. This means, when you're randomly wandering around, you don't get bothered that there are open Wifi networks around and you save the power of searching for them. The downside is that Google Navigation wants to have Wifi on to augment GPS and get a better location, so then you have to go over and "force" your Wifi on. (Since I so rarely use Navigation, it's not a big imposition...)