Caution: Although the courses are in English, they were never designed for foreigners. That doesn't mean Indians are aliens and anyone living outside South Asia will find it impossible to comprehend the books. All I intend to say is that the courses presuppose a knowledge of intermediate English and an Indian language (Hindi). It also presupposes shared cultural references which might or might not be familiar to the reader outside South Asia. For example, the dialogue "Whose elephant is this?" in An Intensive Course in Sanskrit and a discussion on whether prettier actresses work in Manipuri cinema or in Bollywood in An Intensive Course in Manipuri.
Another challenge can be the script and sound. Most major Indian languages have an identical sound repository, similar scripts, and similar ways to express themselves. For instance, ਕ (ka), ਖ (kha), ਗ (ga), ਘ (gha) in Gurumukhi (Punjabi) map to क (ka), ख (kha), ग (ga), घ (gha) in Devanagri. Unsurprisingly, the books don't dwell on writing and sounds much. But this can be easily remedied by looking for alphabet lessons on YouTube.
Enough from me, now you might want to watch Professor Alexander Arguelles' review before jumping in.
Assamese
- भारतीया भाषा ज्योति: असमिया (Beginners)
- An Intensive Course in Assamese (Beginners)
- An Intermediate Course in Assamese
- An Advanced Course in Assamese
Bengali
- भारतीय भाषा ज्योति: बंगला (Beginners)
- An Intensive Course in Bengali (Beginners)
- Lehrbuch der modernen bengalischen Hochsprachen (Beginners; not from CIIL)
- Epar Bangla Opar Bangla: Bangla Across Borders! (Beginners)
- An Advanced Course Reader in Bengali[
- বাংলাপিডিয়া (Banglapedia)
Bodo
Dogri
Gujarati (Gujarathi)
- भारतीय भाषा ज्योति: गुजराती (Beginners)
- An Intensive Course in Gujarati (Beginners)
- An Intermediate Course Reader in Gujarathi
- An Advanced Course in Gujarathi
- ગુજરાતી વિશ્વકોશ (Gujarati Encyclopedia)
Hindi
- Script
- European Languages
- रूसी-हिन्दी कोश (Русско-Хинди Словарь)
- फ्रांसीसी-हिन्दी कोश (Dictionannaire Française Hindi)
- जर्मन-हिन्दी कोश भाग 1 (Deutsch-Hindi Wörterbuch Bund 1) (German: A-F)
- जर्मन-हिन्दी कोश भाग 2 (Deutsch-Hindi Wörterbuch Bund 2) (German: G-L)
- हिन्दी-स्पेनी कोश (Dictionario hindi-español)
- चेक-हिन्दी कोश (Česky Hindsky Slovník)
- African and Middle Eastern Languages
- Asian Languages
- Indian Languages
- This list is going to be enormous. I think I will create another thread for it.
Kannada
- भारतीय भाषा ज्योति: कन्नड (Beginners)
- An Intensive Course in Kannada (Beginners)
- An Intermediate Course Reader in Kannada
- A Manual of Modern Kannada
Kashmiri
- वॅलिव कॉशुर हेछव : हिस-1 (प्राइमर) (Beginners)
- वॅलिव कॉशुर हेछव : हिस-2 (रीडर) (Beginners)
- कश्मीरी स्वयंशिक्षक (Beginners)
- An Intensive Course in Kashmiri (Beginners)
- An Intermediate Course in Kashmiri
- An Advanced Course in Kashmiri
Malayalam
- भारतीया भाषा ज्योति: मलयालम (Beginners)
- An Intensive Course in Malayalam (Beginners)
- Malayalam: A University Course and Reference Grammar
- An Intermediate Course in Malayalam
- An Advanced Course Reader in Malayalam
- സര്വ്വവിജ്ഞാനകോശം (Universal Encyclopedia)
Manipuri
- An Intensive Course in Manipuri (Beginners)
Marathi
- भारतीय भाषा ज्योति: मराठी (Beginners)
- An Intensive Course in Marathi (Beginners)
- An Intermediate Course in Marathi
- An Advanced Course in Marathi
- मराठी विश्वकोश (Marathi Encyclopedia)
Nepali
- An Intensive Course in Nepali (Beginners)
Oriya (Odia)
Punjabi
- An Intensive Course in Punjabi
- ਪੰਜਾਬੀਪੀਡੀਆ (A portal similar to Terms.Naver or Academic.Ru, where you can consult several dictionaries and encyclopedias.) (Not from CIIL)
- ਅੰਗ੍ਰੇਜ਼ੀ-ਪੰਜਾਬੀ ਕੋਸ਼ English-Punjabi Dictionary (Not from CIIL)
- ਪੰਜਾਬੀ-ਅੰਗ੍ਰੇਜ਼ੀ ਕੋਸ਼ Punjabi-English Dictionary (Not from CIIL)
Sanskrit
- Begleitband: Einführung in die Devanagari-Schrift (Not from CIIL)
- An Intensive Course in Sanskrit (Beginners)
- Sanskrit für Anfänger - Ein Lehr- und Übungsbuch: Band 1: Grammatik (Not from CIIL)
- Sanskrit für Anfänger - Ein Lehr- und Übungsbuch: Band 2: Texte, Übungen & Vokabular (Not from CIIL)
Sindhi
- An Intensive Course in Sindhi
- An Intensive Course in Sindhi (Devanagri)
- An Intermediate Course in Sindhi
- An Intermediate Course in Sindhi (Devanagri)
- An Advanced Course Reader in Sindhi
- An Advanced Course Reader in Sindhi (Devanagri)
Tamil
- An Introduction to Tamil Script (Script)
- Lehrbuch des Tamil: Teil 1: Einführung in die Schrift- und Umgangssprache des Modernen Tamil (Not from CIIL)
- भारतीय भाषा ज्यॊति तामिल – 1 (Beginners)
- भारतीय भाषा ज्यॊति तामिल – 2 (Beginners)
- An Intensive Course in Tamil (Beginners)
- Lehrbuch des Tamil: Teil 2: Grammatik, Übungen, Texte und Vokabular (Not from CIIIL)
- Lehrbuch des Tamil: Teil 3: Ergänzende Übungen und Texte (Not from CIIL)
- An Advanced Course Reader in Tamil
- Heidelberg Tamil (Not from CIIL)
Telugu
- भारतीय भाषा ज्योति तेलुगु 1 (Beginners)
- भारतीय भाषा ज्योति तेलुगु 2 (Beginners)
- An Intensive Course in Telugu (Beginners)
- Начальный курс языка телугу (Beginners)
Urdu
[/list]
EDIT. Expanded the sections on Hindi, Sanskrit, and Tamil.