Space

NASA - GO - simply breathtaking accomplishments from this group - they can (& do) take your browser where "no browser has gone before" - & they do it nearly every day. The real time active tracking & video links with current spaceflights should not be missed.

Chandra X-Ray Observatory - GO - gateway to the hot universe of black holes, exploding stars & Galaxy clusters - untangling some of the deepest mysteries in the universe. Great education resources & quality galleries.

Hubble Space Telescope - GO - beautiful images of our universe being born, multimedia, interactive fun & games, Hubble facts & figures.

Imagine the Universe - GO - get the lowdown about our universe in a clear & concise format. Ask your burning cosmic questions, or just sit back & view the great videos of the heavens.

Space.com - GO - reflect on heavenly news, play games, watch videos, track missions & launches, join a community search for extraterrestrial lifeforms.

Solar System Simulator - GO - view the universe from any point of view with this spyglass on the cosmos.
Windows to the Universe - GO - fun & different site about earth & space presented at three levels catering for beginning space cadet, intermediate solar system captain & advanced deep space commander types.

Astronomy Picture of the Day - GO - simple site with daily "pin up photos" for astronomers - with picture bios & links for further research. Archives of specific subjects such as black holes & spiral galaxies.

Ask Dr Universe - GO - the world's most curious cat answers kid's questions about the universe. Dr. Universe answers some of life's most confounding questions.

Bad Astronomy - GO - correcting science myths & solving some puzzling science questions.

The Nine Planets - GO - multimedia tour of the solar system.

Solar System Live - GO - view the universe from any time point or position with this interactive tool - also anearth & moon viewer. 

Home Planet Tracking Software - GO - astronomy & satellite tracking package. 

EarthRise - GO - large database of photos of the earth from the past 15 years.
Non-Messier Objects Database - GO - images of deep space objects.