Only way I've ever been able to take screenies of the phone was to plug it into my computer and run DDMS from the Android SDK. You'd do that by... 1. Downloading and Installing/Unzipping Android 1.5 SDK 2. Navigating to /tools directory and finding DDMS.bat file and running it. 3. Connect your G1 to the computer and it should be picked up in the DDMS. Make sure you have turned on USB debugging in the Settings menu before trying it.
The weather widget is part of the aHome set of available widget ... and it is configurable down to the zip code level.... sorry I missed you post earlier