Anyone who comes from the East End of London (Mile End, Bethnal Green) or New York, or ... anywhere, really, learns some Yiddish. There's Yiddish-the-language, spoken by only a few people now, and there's Yiddish-the-words. Everyone knows some Yiddish words, you might not even realise they're Yiddish. Schmooze, nosh, meshuga, gonif. If you want to know more, go to A Glossary of Yiddish Expressions. Oh, and about the spellings - don't ask. A deigeh hob ich. There is no correct spelling in Yiddish, a gezunt ahf dein kop. If you know better spellings, drai mir nit kain kop.
Thanks to FistMan for the suggestion to make the Yiddish Internet, and for the word list, a gezunt ahf dein kop.
First a warning. Once you gai shoyn these links, you've entered a yeneh velt. You've entered the Yiddish Internet. Words don't always mean what you thought. "A broch tsu dir!" can mean "A blessing on you" or "A curse on you", depending on context and tone of voice. You thought Chinese was difficult?
Here's Diana the Valkyrie's web site, translated into Yiddish. You can browse it, just like you would normally.
Or you can go look at someone else's web site, Yiddish version. Oi vai iz mir! Diana the Valkyrie has translated the entire internet into Yiddish for you, so you can browse around as per usual, but everything will be in Yiddish. Farshtaist? For gezunterhait!