[Photo taken by: ben cooper – http://www.flickr.com/photos/cycleologist/%5D
Proficiency Exams are tests taken by foreigners to assess their knowledge of English, which may be required by some companies. Also, graduate students applying for a Master or Doctor Degree and people who are going to study abroad in a university or for exchange programs may also need them.
The main Certificates of Proficiency are: TOEFL, TOEIC, and the Cambridge ESOL Exams.
Check the sites:
TOEFL – in English: http://www.ets.org/toefl
TOEIC – in English: http://www.ets.org/toeic
ESOL – in English: http://www.cambridgeesol.org/exams/index.ht
ESOL – in Brazil: http://www.cambridgeesol.org/brasil
More information on Exams for Foreign Learns of English can be found in Wikipedia: http://en.wikipedia.org/wiki/English_language_learning_and_teaching#Exams_for_learners
You can find practice tests in this site: http://www.examenglish.com