Running

Content related to running, marathons, etc in Japanese.

Runnet
A portal site for running in Japan, used heavily for race registration but there is a lot of running related content.

ランニング用語事典
Dictionary of running-related terms.

A handful of marathons
東京, 大阪, 那覇, 神戸, ホノルル

ホノルルマラソンポッドキャスト
As of 2012/09 all the discussion was about the 2012 event. Even if they don't continue the podcast it will be a nice resource of marathon-related discussion.

Footwork (running gear/wear)
There are a million stores selling running goods and here is one example.

Wikipedia マラソン
Basic article about marathons.