Although leaving my iPhone 2g on the lawn to get soaked by the sprinklers was a good excuse to upgrade, I've never had the heart to actually throw the broken thing away. I finally decided I might as well try to crack it open so I ordered tools and a replacement battery.
Opening the phone was easier than I expected. All told, I spent about an hour opening the phone, desoldering the old battery, soldering in the new one, and cleaning out some lint with a dental pick and canned air. The phone looks almost as good as new now, although some of the seams aren't quite as tight as they were from factory. Now I want to try repairing all my busted down gadgets.
I cut my fingers a few times on the sharp edges of the aluminum iPhone back, so be careful! Also, use some desolder braid to clean up the pads where the battery is soldered in.
iPhone Gen 1 Replacement Battery
Phillips #00 Screwdriver
iSesamo Opening Tool