If you found Bam&Kero too simple, too boring or too short, I have a something new to read for you today. Aesop's fables are well known all over the word and thus it comes as no surprise that his writings were also translated into Japanese language.
Today's Aesop's Fable (きょうのイソップ童話) is a Japanese website that makes 365 (an entire year of daily reading material!) fables translated into Japanese, available on-line.
Type: Fables collection
Script: All jōyō kanji
The fables are divided into 12 sections—one for each month of the year. The site has a very intuitive user interface and every fable is accompanied with an often beautiful illustration that makes it easy to find a specific fable and to navigate the website even if you don't understand everything that is written on the website.
Most are also available as an mp3 recording which can be downloaded or played in an embedded Flash media player. This is a unique feature that can be helpful both to improve one's reading skills (try listening to the audio and reading at the same time), or in preparation for the JLPT listening section.
While the fables are short, and the website is mainly oriented at Japanese children, the texts definitely aren't easy. The site uses all of the 1,945 jōyō kanji (常用漢字) and you may want to use a furigana (振り仮名) injector such as Hiragana Megane to add readings to the kanji.
If you don't mind foregoing the ease of kanji lookup on a computer and prefer to read on paper, there's also a print version of all the fables over at Amazon.co.jp.
If you are a bookworm like me, try Blinkist. With LinguaLift you get a 20% discount!