http://dayton.hq.nasa.gov/

GRIN is a collection of spiffy NASA images. Lots of cool stuff there, I just steamed through and picked out some of my favorites. All images by NASA. :)

Neil Armstrong with the X-15


Showering in a bag on Skylab


The Apollo 11 astronauts were popular in Mexico City!


Gemini 4: Ed White, first US spacewalk, 1965


M2-F2, early 70's


Crazy planes at the Dryden Flight Research Center


Lunar Lander Research Vehicle, 1964


Tier III Darkstar stealth craft, 1995; crashed on its second flight and was destroyed


17,000 mph impact test--space debris simulation--at the Hypervelocity Ballistic Range


Explorer 24 atmospheric probe, 1964


First picture of Earth and Moon, Voyager 1, 1977


Inflatable space station concept, 1961


Little Joe launch test vehicle, Mercury program, 1959


Apollo 9 lunar module "Spider" in Earth orbit, 1969


Test firing a Saturn V booster, 1967


Apollo 17 astronaut Harrison Schmitt covered in Moon dirt in lunar soil tests, 1972


"Reflection" nebula NGC 1999: shines only due to illumination from another object, rather than from its own hot gases like most visible nebulae


Galaxy NGC 4650A; only about 100 "polar ring" galaxies have been found; their vast outer rings are thought to be the result of a collision with another galaxy


Supernova SN1987A's explosion was visible on Earth in 1987; in a few years we'll see its shock front hit the gases and stars next to it in the Large Magellanic Cloud, which should be fairly spectacular


The "Cat's Eye Nebula," remnant of what might be a dying binary star system


Neptune and its moon Triton from Voyager 2, 1989

Sort of a related note that I'm just filing away here: on the subject of interesting NASA image collections of non-space photos, there's "Visible Earth"

http://visibleearth.nasa.gov/

which is a collection of satellite photos of just about every thing and event on Earth you could imagine a satellite photographing, maybe, aside (I would hope) from top secret stuff and so on.