Comprehensive Yiddish-English dictionary (highly recommended)

by Solon Beinfeld and Harry Bochner

This new dictionary (published just two years ago) is by the far the best resource for Yiddish-English translation and is a wonderful investment. The hard copy costs around £30 or you can access the online version for the same price here:

http://verterbukh.org

A real must if you want to invest in just one book for this module!

There is a review of the dictionary here.