I'm linguistically challenged. Yup. Despite much study, I often find myself at a language loss when I'm actually on the ground elsewhere, which is where I can't function without my well-thumbed travel phrasebooks. They fit in a cargo pants pocket, and I can just hand one over to an exasperated shopkeeper when pantomime and international pictionary fail, as travel phrasebooks have reverse dictionaries. Check out the best of the best travel phrasebooks and dictionaries (scroll to see 'em all):
How I love this one -- when in Mexico, this Mexican Spanish phrasebook is a godsend. Although I did discover once in the jungle of Chiapas that there is no Spanish phrase for, "Do you sell portable personal air conditioners?" that can be understood when uttered by a sweaty, wild eyed babbler. (Yeah, don't think they had that, anyway.)
Spanish words can vary slightly from country to country where Spanish is the language, and this phrasebook lists a word or phrase and how it's said over different borders (un cafecito in Mexico or un cafe chico in Argentina will get you a small cup of coffee; la farmacia is the pharmacy in Mexico -- in Columbia, it's la drogueria). The best travel phrasebooks also provide you with snippets of valuable info about the country, and this one lists things like a brief overview of typical dishes in all Latin American countries or the difference in bullfight rules from Mexico to Costa Rica (just what you needed to know, right?).
You're covered for most of the bases in the EU with a Western Europe phrasebook -- get Danish, Dutch, French, German, Greek, Italian, Norwegian, Portuguese, Spanish, Swedish and even Turkish with Lonely Planet's most excellent Western Europe phrasebook. We like this lots... it's a good one for a group tour, where one may be hitting many countries in a few days ("If this is Brussels, it must be Tuesday... oh, wait, where's the Flemish phrasebook?"... naw, seriously, you'll be fine in most of Europe, where many locals speak a smattering of other tongues, with this catch-all book).