Avivale's Yiddish Page: A personal web page about the Yiddish language.
Der Bay - Anglo-Yiddish Newsletter: International Anglo-Yiddish newsletter/website with international kalendar, with news of klezmer bands, Yiddish teachers, yiddish clubs, and translators.
Der Yidisher TamTam: From Paris, a Yiddish newspaper geared toward students of Yiddish, downloadable in PDF format.
How To Talk Jewish: A humorous site that reaches into Jewish ethnicity with an alphabetical listing of popular Yiddish words and phrases along with insight into the history of the language
Sheva Zucker's Yiddish: Information about the text book "Yiddish: An Introduction to the Language, Literature & Culture" and its accompanying audio-cassette series by the author herself.
The Yiddish Typewriter / Di Yidishe Shraybmashinke: Lets you compose a page of Yiddish text from your web browser. Also converts between a growing list of Yiddish computer file formats and character encodings.
Tsuguya Sasaki's Cyberia: Website on Hebrew and Jewish languages and linguistics, including brief descriptions, bibliographies and links to other online resources
Yiddish Transliteration: Yiddish Transliteration a.k.a. Romanization as standardized by the YIVO Institute. Also useful as a guide to the Hebrew-alphabet-based writing system traditionally used for Yiddish. (From Shtetl.)