Miscellaneous such as mathematics and / or metaphysics 

Nice online calculator (website in German): http://web2.0rechner.de:

A true random number generator which is based on atmospheric noise: http://www.random.org  

Projective geometry and its relations to other branches of science and metaphysics: http://www.nct.anth.org.uk 

Website of Dr. Stephen M. Phillips about sacred geometries, physics and metaphysics: http://www.smphillips.8m.com