Source-highlight, given a source file, produces a document with syntax highlighting. [Open source, GPL]

Acts as a caching pre-processor to C/C++ compilers, which often results in a 5 to 10 times speedup in common compilations. [Open Source, GPL]

Cscope is a developer's tool for browsing C programming code.

Source-to-source translator for C, which analyzes the program to determine the smallest number of run-time checks that must be inserted in the program to prevent all memory safety violations.

KScope is a KDE front-end to Cscope. It provides a source-editing environment for large C projects, such as the Linux kernel. [Open source, GPL]

Tool for statically checking C programs. [Open source, GPL]

Splint is a tool for statically checking C programs for security vulnerabilities and coding mistakes.

A static analyzer analyzes reactive, critical, real-time programs written in the C programming language and looks for runtime errors.

CodeViz provides the ability to generate call graphs to aid the task of understanding code. [Open Source, GPL]

Cxref is a C source code cross referencing and documenting program for UNIX, written by Andrew M. Bishop. Cxref makes both html and latex style document.