Lingvosoft provides Yiddish translation software for Windows and PocketPC. You can download trial versions, to see what works best for you.

The offerings for Yiddish are slim, but what we do have what most people are looking for. That would be the...

Yiddish Talking Dictionary (just under $50). This is what most people are looking for. Load this on your machine, and you have a virtual translation device. It delivers instant bi-directional translation of all the words and phrases in its massive database.
More info: PocketPC version | Windows version
 

You might also want to obtain the....

Yiddish Picture Dictionary for Pocket PC (just under $40). The Ectaco KwikPoint program is an effective and easy to use system for getting your ideas across–silently! Featuring more than 600 universally recognized symbols, it helps you communicate in many different situations without speaking a single word. It  lets you communicate your needs concerning dining, lodging, transportation, and other commonly encountered situations with a minimum of effort. Simply select the picture you want and show it to your waiter, hotel clerk, bus driver, or even your new best friend. Providing essential travel tools for your personal and professional needs, it allows you to interact with the people you meet on your trip abroad and to be understood! Make new friends and enhance your travel experiences now with this user-friendly communication tool for the whole family! More info