This is the site of Harvard's Writing Center. This site contains excellent advice on writing argumentative essays. (
http://www.fas.harvard.edu/~wricntr/index.html
)
This site contains a writing manual for writing effective philosophical papers. There is some excellent advice here on how to improve the effectiveness of your arguments and avoid many of the pitfalls common to student papers. (
http://eee.uci.edu/programs/philoswr/
)