manageability

http://www.manageability.org/blog/stuff/open-source-document-repository/view

Good article on jack-rabbit: http://www-128.ibm.com/developerworks/java/library/j-jcr/

Yet another good article. http://www.artima.com/lejava/articles/contentrepositoryP.html

http://blog.gmane.org/gmane.comp.jakarta.log4j.user/month=20021001

Testing using mock objects and static code analysis
Findbugs -- can be found on sourceforge
Marmoset project -- can be found on sourceforge