Test Your English Fluency/Slang/Idiom... in Online

http://www.english-test.net/

Some Sample Test Topics are...

• English Grammar Exercises
• English Synonym Worksheets
• Business English Tests
• Common Errors in English Usage
• Idiomatic Expressions in English

Some of useful business english learning websites...

http://llbest.com/Idioms.htm
http://www.englishdaily626.com/idioms.php
http://www.paulnoll.com/Books/Clear-English/English-idioms-01.html
http://iteslj.org/links/ESL/Idioms_and_Slang/
http://www.answers.com/library/Idioms
http://www.rong-chang.com/idioms.htm
http://www.scit.wlv.ac.uk/~jphb/american.html
http://www.learn4good.com/languages/evrd_idioms/id-b.htm
http://www.idiomsite.com/