This is a list of links with useful resources:

Atomic Rocket

http://www.projectrho.com/rocket/

HyperPhysics

http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

Martin Fogg's Terraforming Information Pages

http://www.users.globalnet.co.uk/~mfogg/index.htm

MarsDrive

http://www.marsdrive.com/

Mars News: NewsWire for the New Frontier
http://www.marsnews.com/

NIST Chemistry WebBook

http://webbook.nist.gov/chemistry/

Red Colony
http://www.redcolony.com/

Rocket and Space Technology

http://www.braeunig.us