Developer website: EGO Systems, Inc.
Fortunately, Apple has finally given us a way, in the form of a .plist file, to change these settings. Unfortunately, taking advantage of this has meant a trip to the terminal every time you wanted to alter either setting.
Our Screenshots Preference Pane was written to make these Terminal sessions unnecessary. It allows you to change both the file format of your screenshots as well as where they end up on disk, with just a few clicks of the mouse.
*Previously available here