From Learning Japanese Wiki (RtKWiki)
- TxtMiru A Japanese novel viewer. Supports vertical text. Supports aozora formatting. Highly configurable. Bookmark feature. Doesn't require installation. Text is fully selectable. The default text size is very difficult to read on a netbook-sized screen but it should be acceptable on a normal-sized desktop display. See the forum to learn how to change the default layout.
- ArisuViewer Another Japanese novel viewer. Supports vertical text. Supports aozora formatting. Bookmark feature. Doesn't require installation. The text is NOT selectable!
- Dinglabs Desktop Player Offline player for reading and listening to audiobooks with transcripts. 
- JNovel Formatter A utility to convert Japanese novels to nicely formatted HTML files. For Windows.
- 青Ｐ A Japanese program that will turn a Japanese novel into a nicely formatted PDF file with vertical text support. Highly configurable. Supports aozora formatting. See the forum for more information.
- Aozora to Kindle - Online tool that converts Aozora-formatted books to Kindle-friendly .pdf files, with ruby and vertical, selectable text.
- AozoraEpub3 ( 青空文庫ePub3変換 ) Utility that takes any text, in any encoding; zipped collections of images; and urls and converts them to an ePub file. You can even choose between vertical or horizontal text. See the forum for a quick guide on how to use it.
- dotEPUB (Chrome extension) Extension that allows you to convert any webpage into an EPUB or Kindle e-book.
- Easy method for creating Epubs, AZW3 with Furigana (2015 January 22)
- cb's JNovel Formatter (2011 February 07)