The Big Picture
If you want hi-res images which cover almost everything under the sky and up in the sky, then The Big Picture at Boston Globe is the place to go (I’ve added the link to the sidebar).
Really, the images there are incredible! They showcase the cultures of different countries, religions, history, art, health, nature, environment, natural disaster (such as volcanoes, hurricanes, and earthquakes), war, sports and the beauty beyond our planet.
Take your time and slowly go through the archives (which is quite a lot, but I think is very much worth your time, trust me, you’ll not regret it). But personally, I would like to highlight a few of my favourites (and of course, I’m biased, they are mostly astronomy related…)
p/s: all these images are hi-res, so it may take some time to load, but it’s worth the waiting.
The Sun
View of Jupiter
Total Solar Eclipse of 2008
The Baikonur Cosmodrome
The Sky from Above
Hurricane Ike
Peering into the Micro-World
The Large Hadron Collider