Runner's World   This is a great site featuring running news, pace calculators, records and statistics, training schedules, nutrition information, and many other helpful resources.
Hal Higdon   Hal Higdon is a popular running writer. His site features training guides tailored for novices through advanced runners. They range from 5K guides up to ones for ultramarathoners. Visitors can read articles and columns he has written about running or order one of his many running books.
Road Runners Club of America   This is an organization many local running clubs belong to. It produces a nice newsletter/magazine called Footnotes that it puts on its site for anyone to read.
The Running Network   If you're looking for running clubs in your area, this site has a list of them by state and city. It also has a list of running stores, training tips, and running news.
Active   This site features a race calendar. It allows you to sign up and pay for races across the country through its system.
Running Times   The Running Times site contains current American and world running rankings, guides to energy bars, shoes, and race training, and an index of informative articles.