NearOCR is an OCR program based on NearNeural, and was written as a first-year project in Java. It uses a series of sensor vectors to learn the ideal shape of letters from a training corpus before comparing those identified in a document against this gold standard using the neural net (and a covariance measure).
The code is relatively clean, but since I was only young and impulsive it might not be the highest quality work ever. The fact that it's a pure-Java open source OCR tool and library probably makes it best suited to use as an educational tool.
Download NearOCR-0.1.tar.gz.
The download comes with a series of scripts, compile, document and run. Run these for their respective functions!
When it comes to using the tool, the following is a rough outline:
There is a help file in the help/ folder, which can be opened using anything that supports ODF, as well as a report in html format, written for the project.
The OCR and neural net parts are both libraries, used by a front-end written in Swing. The javadoc is here.