One of the best general sites on Hinduism and related topics has pages on many topics with an easily accessible index to all of the pages. Both philosophical and practical aspects are covered.
Many of the classics of Hinduism and Advaita are available as public domain downloads at the Internet Sacred Text Archive, including the Vedas, Upanishads, Mahabharata and Ramayana.
India Divine - has general information on Hinduism and scriptures with articles, downloads, screen-savers etc. Audio lectures on Vedanta may be heard on-line or downloaded. There are bi-monthly newsletters published by Bhaktivedanta Ashram in India and much more.
Hinduism Online is another large site specialising in all topics relating to Hinduism.
Gems From The Ocean Of Traditional Hindu Thought
Prof. V. Krishnamurthy had made extracts from his books available here. There are a wide range of topics relating to Hinduism in general and Vedanta in particular. ProfVK (as he is known) has now compiled and ordered the material into a single book, which is being made available in PDF format. This may be viewed (and saved locally as required) from the Advaitin.net site. There are a wide range of topics relating to Hinduism in general and Vedanta in particular and it can be highly recommended.
Shri Kanchi Kamakoti Peetham - contains lots of general information on Hinduism. In particular, there is an English translation of two volumes of 'Hindu Dharma' from the Tamil, containing talks on many subjects by Sri Sri Sri Chandesekharendra Saraswati Mahaswamiji. There are also a number of articles by various people on, for example, the life and teaching of Shankara. Five hours of audio and video are also offered.
HinduWiki was begun in Sept 2006 with the ambition of containing all information relating to Hinduism, set up and maintained by users of the site in the same manner as Wikipedia. Looks very promising if it receives the necessary level of support.
An excellent hierarchical index of a great many sites may be found at the Khoj India Directory.
Vedic Life is a huge website for all aspects relating to the Vedas as well as information and links relating to Spiritual Masters and Ashrams.
For a massive site on all things to do with India, including religions and scriptures but also history, culture, economy etc. see bharatadesam - everything about India.
A free, on-line book all about
Hinduism is available at Sri Kanchi Kamakoti
Dharma" by Sri Sri Sri Chandrasekharendra
Saraswathi MahaSwamiji. This comprises two volumes
of speeches from the Tamil Book "Deivatthin
vedamu.org is a site devoted to Vedic literature, as well as other subjects ranging from Vedic astrology and Vedic chanting, to courses in learning Sanskrit. A wealth of highly useful information.
intellectualhinduism.blogspot.com is another blog containing an abundance of information on Hinduism, including the sages Adi Shankaracharya and Vivekananda, as well as textual resources on the Ramayana, the Mahabharata, the Upanishads, the Bhagavad Gita and many, many more. Another highly recommended site.
Indian Philosophy and Religion provides links to sites of general interest on Indian religions; publishers of related books and relevant E-Groups. There is a list of pointers to sites containing texts of many of the Upanishads, the Gita and the Brahmasutra and other texts such as the Astavakra Gita and Patanjali Yoga sutras. There are links to traditional schools and temples etc. as well as modern schools.