Here are some key resources for teachers and student journalists. Many thanks to my friend Steve Chiger (former president of GSSPA) for these leads!
The Garden State Scholastic Press Association is New Jersey's non-profit support organization for advisers of high school and middle school publications, as well as for student journalists and editors. Operating multiple conferences each year, the group sponsors grants and mentorship for teachers and scholarships and contests for students. Their resources directory features more than 200 links and is fully searchable -- the most robust of its kind.
Founded in 1924, the Journalism Education Association is the only independent national scholastic organization for journalism educators. The group operates a teaching listserve where journalism educators around the country share ideas and materials. In addition, its bookstore contains a trove of teaching materials and resources for instructors -- essential for those looking to build or develop a program. Among JEA's 2,100 members are journalism teachers and publications advisers, media professionals, press associations, adviser organizations, libraries, yearbook companies, newspapers, radio stations and departments of journalism.
Other sites of note:
Journalism Resource Center (Thanks to Melissa Taylor for this great addition!)
National Scholastic Press Association
Deal News/Online Daily News Source provides links to the major online newspapers in America with brief descriptive notes about them. (Thanks to Susan Brown for this lead!)
For more information on plagiarism, copyrights, and citing sources (esp. online sources), this Webpage has links to more than a dozen useful Websites.
The New York Times provides many resources for student use. Check out, for example, the Learning Network, and this post on "10 Ways to Teach Argument Using the NY Times."