popShot

Fresh, minimal, and handy, popShot is built with focus on the user experience. Effortless, quick, and clutter-free screen-grabbing, an intuitive interface, ease to use -- and with extra functions implemented to avoid a desktop crowded with heaps of almost identically labelled files.

There's also a Grab to URL function built on the same principles: "It just works." No set-up, subscriptions, logins, or knowledge needed.