SnapNDrag (Free).

Screen Capture made easy.

Effortless Screen Capture

SnapNDrag lets you take a screenshot by just clicking a button and dragging the resulting screenshot off.

For example, to email a screenshot, you would drag the screenshot from SnapNDrag to the Mail application. It is that simple. No hard-to-remember key combinations, no file conversion to deal with, no file dialog boxes to navigate, no temporary files to erase later on.

Multiple Formats

Supports PNG and TIFF for times when image quality cannot be compromised. Or use JPEG with adjustable quality for smaller file sizes.

Get it here.