新日本古典籍総合データベース（国文学研究資料館）
Database of Pre-modern Japanese Works is compiled, with an intention to provide about 100,000 digitized images accompanied with 600,000 bibliographic information stored at different institutions in Japan, by the National Institute of Japanese Literature (NIJL) whose website, https://www.nijl.ac.jp/en/ also provides all kinds of beneficial information about Japanese literature in English as well.
和歌データベース（国際日本文化研究センター）
Waka database is compiled by the International Research Center for Japanese Studies (Nichibunken), whose website, http://www.nichibun.ac.jp/pc1/en/, also works as a good companion for any researchers for Japanese literature. This database also enables searches for Haikai (俳諧), Renga (連歌), Renga renso goi [associated vocabularies] (連歌連想語彙).
日本語テキストイニシアチブ（バージニア大学・ピッツバーグ大学）
In case you have any specific titles of Japanese literature in your mind, please use the link above. You can find English explanations about each work as well as the original text in Japanese.