Recently I've come across a very good website on Tantra in Hindi. You'll get a lot of knowledge about Tantra theoretically through this website. Here's the link :
तंत्र : एक परिचय
My blogic attempt to unfold the secret of Indian philosophies and bringing it's spiritual teachings to the common men. Some of the topics covered are Ayurveda, Jyotisha, Yoga, Tantra, Vedanta, Hinduism, and Buddhism etc.