Also, another Sanskrit site has information about the ITRANS transliteration system. At the ITRANS site, you can send off transliterated material, and in about a minute get back a nice devanagari version of your text. Click here for a sample of ITRANS format.
The Zoroastrian archives give Avestan texts and information on Zoroastrianism.
Many Old English texts (including Beowulf) are available here, along with materials for a course on Beowulf. The Old English texts can be searched by way of labyrinth, where a number of other materials (Middle English, some Latin, etc., can also be found.
This gives a listing of institutions in North America where "uncommonly taught languages" (such as Sanskrit and Avestan) are offered. Almost every language is listed here; my impression is that only English, French, German, and Spanish are omitted (and one can find "Old" stages of all four).