Mantras are an unique feature of the Indian religions. Though sometimes (incorrectly) rendered as "Spell" in English, there is no exact equivalent of the term in the English Language. Mantras are generally in Sanskrit, but some Jaina Mantras have them in Prakrit forms such as Ardha Magadhi.
It is very interesting to note that Mantras are relied on Vedic Tradition which stresses importance on strict pronunciation and also in the Buddhist Traditions, where the pronunciation of the Mantra has become nativized, completely straying away from the original Sanskrit. But still, Mantras are relied upon on in all these traditions.
The Mantra Section of this site is strongly inspired by Visible Mantra. The presentation could be more or less like in the same manner. I have tried to make it unque and different, but the influence of the site refuses to subside !.
There is the separate section on Mantras in the Weblinks page, which can be checked out too.