Yantra

https://en.wikipedia.org/wiki/Yantra

Site
http://www.sriyantras.com/

Kart
https://www.yantrakart.com/

Yoga
http://www.yantrayoga.net/ 

Shastra
http://www.yantrashastra.com/

Centre
http://sripyramidyantracenter.blogspot.com/

images
http://www.yantraimages.com

Tube
https://www.youtube.com/results?search_query=yantra 

Slides
http://www.slideshare.net/search/slideshow?searchfrom=header&q=yantra