Free Online Resources for Indo-Europeanists
Classics
Diogenes - environment for reading and searching through texts in Latin and Ancient Greek that includes dictionary support
Indic
Sanskrit Library - This website is full of useful resources including a page that allows you to search multiple dictionaries at once and compare entries. Control which dictionaries you see under "Preferences".
Rigveda Translation Commentary (Stephanie W. Jamison)
CPD - Critical Pāli Dictionary
The Pali Text Society's Pali-English dictionary
Turner's Comparative dictionary of Indo-Aryan languages
https://tipitaka.org/ - searchable and downloadable Pāli Canon
Anatolian
HPM - The Hethitologie Portal Mainz
CTH (Catalogue des textes hittites, ed. E. Laroche, cont. S. Košak andG.G.W. Müller)
StBoT (Studien zu den Boğazköy-Texten)
ACLT (Annotated Corpus of Luwian Texts)
Cuneiform Luvian Lexicon (H. Craig Melchert)
eDiAna (Digital Philological-Etymological Dictionary of the Minor Ancient Anatolian Corpus Languages)
Germanic
Bosworth-Toller Anglo Saxon Dictionary
Cleasby-Vigfusson Icelandic Dictionary
EWA - Etymologischen Wörterbuch des Althochdeutschen
ONP - Dictionary of Old Norse Prose
Wulfila Project - digital library dedicated to the study of the Gothic language and Old Germanic languages in general.
Corpus of Middle English Prose and Verse
EDD - Joseph Wright's English Dialect Dictionary,
DW - Deutsches Wörterbuch von Jacob Grimm und Wilhelm Grimm
RuneS - Runische Schriftlichkeit in den germanischen Sprachen
Celtic
eDIL - Electronic Dictionary of the Irish Language
https://www.teanglann.ie/ga/ - A dictionary of Modern Irish
GPC - A Dictionary of the Welsh Language
A Welsh Grammar, Historical and Comparative by John Morris-Jones
Armenian
Նայիրի - Classical Armenian dictionary
https://arak29.org/category/language/
EANC - Eastern Armenian National Corpus