Really nice 3D Flash app visualising the solar system and star charts.

"The Hertzsprung–Russell diagram is a scatter graph of stars showing the relationship between the stars' absolute magnitudes or luminosities versus their spectral types or classifications and effective temperatures."

Watch in HD if you can. Wow.

" Introduction astorb.dat is an ASCII file of high-precision osculating orbital elements, ephemeris uncertainties, and some additional data for all the numbered asteroids and the vast majority of unnumbered asteroids (multi-apparition and single-apparition) for which it is possible to make reasonably determinate computations. "

Public domain javascript functions for converting between different calendar types (Julian, Gregorian, Islamic, Hebrew, Persian, Mayan, Bahai, French, Indian).

"The Astrometry.net robot makes astrometry much easier! It finds photos of the night sky on Flickr and automatically annotates them with astronomical information using notes and machine tags." ... That. Is. Neato!

The mind boggles. Really enjoyed reading this Python astronomy library tutorial :)

"Tell us the date and location of a special moment and we'll calculate the position of the stars, planets, and moon, and then recreate that night sky on a beautiful fine art print"

6 month pinhole camera exposure. I never knew this was something people did!

Harry Beck style astronomical map.

"A catalog of NASA images and animations of our home planet"

"they never forgave those pesky Aussies who stole a march on them and saw the pictures of Mars first. "

"This site is developed and maintained by John Walker, founder of Autodesk, Inc. and co-author of AutoCAD." – all kinds of algorithmic/scientific goodies.

Presentation on NMM's mobile-friendly night sky web-site (via foe).

It's... like... it's... right... there...