The Art of Crossing Cultures, by Craig Sorti (Nicholas Brealey Publishing). What it takes to encounter a new culture and succeed; how to deal with country and culture shock. Equally helpful for business people and exchange students.
The Whole World Guide to Culture Learning, by Daniel J. Hess (Nicholas Brealey Publishing). Handbook for cross-cultural adaptation through experience-based culture learning.
The Whole World Guide to Language Learning, by Terry Marshall (Nicholas Brealey Publishing). On site guide for language learning, whether you enroll in formal language classes, working language learning into a busy schedule, or something in between.
For information about specific cultures, a good place to start is the series, CultureShock-USA-Survival-Etiquette-(Marshall Cavendish Corporation). These reference books provide concrete, practical tips about the customs and etiquette of various countries and cities.