Sports Illustrated has just made its past issues available to read for free from its archives: http://vault.sportsillustrated.cnn.com/
The SI archive includes a wealth of great running articles-- including contemporary coverage of Steve Prefontaine, Gerry Lindgren, and Bill Rodgers-- who made 2 Sports Illustrated covers after winning the New York (and Boston) marathons. There is also great coverage of the great milers and mile races. (Up until the 80's runners had a decent chance of making SI's cover). Besides the covers you can also view the photos that accompanied the articles. There is great coverage of the NCAA cross country championships, indoor track, the Olympics and Track and Field World Championshipships as well as major road races.
You may notice that Sports Illustrated was once a much more eclectic and literary magazine, featuring Faulkner, Hemingway and Olympian Kenny Moore and Hunter S Thompson among its writers.
It was also not that unusual to see show dogs and a wide variety of sports featured on the cover in the early years.