libtap is a C implementation of the Test Anything Protocol, which allows for heterogeneous test suites in several languages.
strace is a useful diagnostic, instructional, and debugging tool. System administrators, diagnosticians, and troubleshooters will find it invaluable for solving problems with programs for which the source is not readily available.
Software to monitor for open files on your system in real time.
A tool that creates DocBook XML from Javadoc or HTML and transforms DocBook to various output formats.