Jamie sent us a really good site on materials and textures the other day. i think its worth recording it on here. http://www.mayang.com/textures/ some other usefull sites that may be handy are as follows
http://www.soton.ac.uk/~imw/Geology-Britain.htm good on geology around Britain
http://www.environment-agency.gov.uk/ good on environment relations e.g floods
http://www.thecarbontrust.co.uk/carbontrust/ good on carbon relations, e.g climate change