Dartmouth Writing Program
http://www.dartmouth.edu/~writing/materials/about.shtml
University of Wisconsin-Madison Writing Center
http://www.wisc.edu/writing/Handbook/

As students begin to return to college campuses across the country, they may
be curious to know that there are a number of fine online resources that
will help them develop their college-level writing skills. The first site
offered here comes from the Dartmouth College Writing Program, and contains
a number of helpful materials, such as some well-written  essays that answer
the question "What is an academic paper?" and also provide information on
researching topics for papers. The site also includes information on such
topics as writing about film, writing for sociology courses, and helpful
suggestions on writing from fellow students. The second site is offered by
the University of Wisconsin-Madison's Writing Center and contains material
on how best to cite references and avoiding common grammar and punctuation
mistakes. Taken together, these sites provide a host of materials that will
allow students to become better writers in their various courses during
their time in the world of higher education and beyond.
 UsingEnglish.com [pdf]
http://www.usingenglish.com/

As more and more persons are seeking high-quality English as a Second
Language (ESL) resources, a number of sites have sprung up to provide just
such materials. One notable site is UsingEnglish.com, which provides grammar
glossaries, reference sheets on irregular verbs, phrasal verbs and idioms,
teacher handouts, and ESL forums. The forums are particularly useful, as
registered users can post questions in the “Ask a Teacher!” feature, and
receive a response from one of their team of expert advisors. The articles
area contains short pieces on using punctuation properly, teaching English
in South Asia, and formal letter writing. The site also has its own weblog,
which contains brief musings on various elements of the English language
that may be helpful both for ESL teachers and those seeking to learn the
language.