Yiddish glossaries can be found at many websites that focus on the Ashkenazic Jewish community, including Kehillat Israel and The Gantseh Megillah, as well as at some general Jewish culture websites such as Judaism 101. Yiddish was the international spoken language of Ashkenazim, the Jewish people of Central Europe.
Kehillat Israel is a reform congregation that hosts a large glossary of Yiddish words on their website. In addition to single words and their definitions, they list curses and insults, as well as aphorisms and proverbs. The Judaism 101 glossary includes Yiddish expressions, as well as words and phrases from other Jewish languages, such as Hebrew and Ladino.
The Gantseh Megillah website is the online face of a magazine that focuses on American Ashkenazic issues. The site includes a glossary of Yiddish expressions and idioms.