Teach English in Japan

There are many native English speakers working at English conversation schools in Japan.
Usually BA is required but any BA is acceptable.
Still it depends on each school and you need to take English test to be hired.
List of famous English conversation schools.

NOVA
More than 900 bruches all over Japan and more tha 480,000 students.
This company procides their own system called "Ginga net" which is using IP TV phone system.
They provide lessons in 7 languages including English, Chinese, Korean, French, Spanish, Italian and German.
URL: http://www.nova.ne.jp/global/index.html

ECC
They provide lessons in 7 languages including English, Chinese, Korean, French, Spanish, Italian and German.
URL: http://www.japanbound.com/

AEON
They provide lessons in English only.
URL: http://www.aeonet.com/

GEOS
They provide lessons in 6 languages including English, Chinese, Korean, French, Spanish and Italian.
URL: http://www.geoscareer.com/

Gaba
They provide lessons in English only.
URL: http://www.gaba1to1english.com/

Berlitz
URL: http://recruit.berlitz.co.jp/

SHANE ENGLISH SCHOOL
URL: http://www.shane.co.jp/

Further resources:
You can join the english teachers community to do some more research.
Teach English in Japan provides useful infomation and you can join community.