You can set the type of image created by typing the following in Terminal:
defaults write NSGlobalDomain AppleScreenShotFormat [imageFormat]
where [imageFormat] can be JPEG, TIFF, PNG, or PICT (TIFF is the default). It's likely you'll have to logout/login to get the changes to take effect.
[ 11-13-2001: Message edited by: Sinewave ]</p>