This is semi-old news, and I've been meaning to mention it, so here ya go: NASA has put up a vast archive of space images on a site they named, for some reason, NASA images.
They have a ton of very cool images there, I must say. When they load, they are fitted to your screen, but then you can zoom in or out, which is fun. There are descriptions on the sidebar (generally tapped from the press releases, looks like) and there are animations as well. There are some nifty gizmos, like an "Embed This" link with pretty clear instructions on how to embed a given picture into a blog or web page --I embedded an illustration of the New Horizons spacecraft by my friend Dan Durda above -- and of course there is the ubiquitous "Share This" link, too.
All in all, well done! It's nice to see some folks at NASA figuring out this whole intertoob thing and doing a nice job of it. Kudos!