WRITING LETTERS

You can watch the following videos about the differences between FORMAL and INFORMAL letters.

http://www.youtube.com/watch?v=BA5mdWZi7T0
http://www.youtube.com/watch?v=1Z9G71G2OBg


To explain the differences between the letters in a very simple and visual way you can look the information that appears in the following link as well,
http://www.schooltrain.info/english/letters/letters_formal.htm

Samples of formal/informal letters,

http://jobsearch.about.com/od/morejobletters/Resignation_Letters_Thank_You_Letters_Employment_Letters.htm

Samples of e-mails

http://www.qgroupplc.com/category/writingemails