This page offers links to a multitude of Jewish Encyclopedias. They will be of great resource to you and even more so to a student or congregant.
Encylopedia of the Founders and Builders of Israel
Encyclopedia of Jewish Medical Ethics
Jewish Encyclopedia English
This site provides an online version of the excellent but now dated Jewish Encyclopedia.
Jewish Virtual Library English
YIVO Encyclopedia of the Jews of Eastern Europe
This encyclopedia is fairly up-to-date. Plus, if you do a search and the topic is not found in the encyclopedia, they put the term in the “work-list” of articles that need to be written.