Travel Etiquette
As you are traveling around the world, knowing a bit about your host country can be valuable. It can help you avoid embarrassing situations or it can help you close that business deal.
This is where websites like Travel Etiquette (via Lifehacker) or Buzzle come in handy. The descriptions for the countries and cultures I personally know are very good and precise, and I would definitely recommend everyone to read up on the places you will be visiting.