Aozora Bunko 青空文庫: Public domain literary and non-fiction works in Japanese. 青空キンドル is a website that converts Aozora files into appropriately-sized PDFs for the Amazon Kindle.
国立国会図書館デジタルコレクション: This is a page that has a collection of digitized documents published since the Meiji era.
includes articles of world news, news from Japan, essays/column, finance, politics, sports, etc., with definitions in English/Japanese. Translation function included.