Using the GNU IMP (GNU Image Manipulation Program) and I couldn't figure out the equivalent to the Photoshop™ Information palette.
The marquee tool in GNU IMP is darned fine, easy to use and resize in all directions, way better IMHO than Photoshop. But I needed to know the size of the marquee I'd created.
A quick look in the manual, and there it is. In the Tool Options palette.