Here's a really good, comprehensive link:
Free Primary Jewish Sources and Resources on the Internet divided in the following manner:
Section_I:_Tanach_and_Chazal/Geonim-era_(up_to_1000_CE)
Section_II:_Rishonim_(1000_CE_to_1492_CE)
Section_III:_Acharonim_(1492_CE_to_present)
Section_IV:_Encyclopedias,_and_Articles_Collections
Section_V:_Tefillot_and_Siddurim
Section_VI:_Tools,_News,_and_Dictionaries
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