What Yiddish dictionary should I get?

Two English transliterated Yiddish dictionaries are Yiddish Dictionary Sourcebook by Galvin and Tamarkin, and A Yiddish Dictionary in Transliteration by Coldoff. The standard is Weinreich's Modern E-Y and Y-E Dictionary. For Hebrew words in Yiddish, both Niborski's and Jacobson's dictionaries are recommended. A full list can be found at the Shtetl.