I am moving to Korea soon and am looking for good resource books for activities and ways to teach english efficiently to foreigners. Thanks!
I will be teaching elementary age children.

Wikipedia

Start with pre-K or K-1 level books that explain the difference between capital and lower case letters, as Korean does not have this distinction. The "Spectrum" series from McGraw-Hill children's publications is a good source. It can help the students to know that they are working at close to the same grade-level as their American counterparts.

Spectrum also published vocabulary books, with a lot of vocabulary organized by theme.

Most important, for conversation, is to teach the children words nd phrases that are germane to their daily life. A young kid under 12 could care less about banking and finance words, or airplane words, but would probably be interested in words such as classroom vocabulary, school subjects, family members, food, animals and places in town. Other good themes include toys, games/sports. You may also want to bring a CD with children's songs in English on it. Singing is a great way to teach proper pronunciation.

My experience with children learning a foreign language indicates that children learn by doing rather than by rote. If they can put what they learn into practice immediately, then they will retain it better.