Here are more links that I thought are useful or inspiring:
Worldbuilding:
Maps and Cartography:
- Sci Maps – Awesome maps about all kinds of scientific topics.
Worlds on the Web:
- This Orb – Creating a science fiction planet in great – and realistic – detail
- The Torn World – Has some nice maps and artwork, worth checking out
Math
- Space Math – Travel times – How long does it take my spaceship to go a given distance?
- Angular Size Calculator – How big is something in the sky?