Capture PNG Screenshots
This is a simple Automator workflow for MAC OS X that allows you to capture screenshots in the PNG format. You can add it as a service or export it to a standalone app for easy access via Spotlight.
Grab app is fine, but it kind of forces you to save things in the TIFF format. This solves that problem by creating screenshots directly in PNG.
Currently it triggers a dialog to capture a selection screenshot rather than a full window. It then saves it to your /tmp folder with a timestamped filename.