Gayatri Pariwar has published several important literature and made them available online, including the 4 vedas and Upanishads.
Inspired by the HMEC's vision of sharing ideas and resources as well as networking in the view of larger interest of Sanatan Dharma, Gayatri Pariwar has made available All four Vedas, 108 Upnishads and other Arsh literature for online reading to all.
Availability on this literature online is so important, please spread the word around. Currently most of it is available in Hindi. But a good start ...
Ved , Puran ,Upanishads and Darshan
Many more books in Hindi and English by Pt Shriram Sharma Acharya