I have an old 1G that is still very usable. Take a look at this:
http://whited00r.com/
I disagree with the previous poster that the 1G can't run 3.1.3 very well. In my experience, it runs great. But it's also very limited by iOS5 & iOS6 standards. Whited00r is a custom firmware that runs 3.1.3 but operates likes 6.0, and it does so very smoothly on my 1G. It's pre-jailbroken, so you have the usual AppStore, Cydia, and one called Time Machine. TimeMachine is an ApPStore that has tons of older AppStore titles that were made for the 3.x firmwares, so you still have access to a ton of apps.. The onyl real limitation to this is you still won't have multi-tasking like a new device, nor will most current app versions (because they are now made for 6.x and higher).
