The Boehm-Demers-Weiser conservative garbage collector can be used as a garbage collecting replacement for C malloc or C++ new. It is also used by a number of programming language implementations that use C as intermediate code. Alternatively, it may be used as a leak detector for C or C++ programs. A slightly older version of the garbage collector is also included as part of the GNU compiler (gcc) distribution.
ltrace is a debugging program which runs a specified command until it exits. While the command is executing, ltrace intercepts and records the dynamic library calls which are called by the executed process and the signals received by that process. It can also intercept and print the system calls executed by the program. The program to be traced need not be recompiled for this, so you can use it on binaries for which you don't have the source handy. You should install ltrace if you need a sysadmin tool for tracking the execution of processes.
Fossil is a distributed software configuration management/version control system built with reliability and ease of use on mind. It comes with integrated bug tracking and a wiki. It is distributed as a single static binary for easy installation and the ability to run in a chrooted environment. Other highlights include a Web interface, autosync, simple networking, and CGI support.
NoBug is a library which provides assertions, logging statements, and annotations for C and C++ programs. It includes pre-/post-condition and invariant checks, as well as generic assertions. Checks are enabled based on build-levels and scope tags. It also includes debugger support (valgrind), dumping of data structures, logging your application's activities, runtime customizable logging via environment variables, different logging targets (ringbuffer, stderr, syslog, debugger, etc.), and annotation of your source code regarding known bugs, things to do, and planned things. It can track resources and detect deadlocks.
CUT is a unit-testing framework for C, C++, and Objective-C. Unlike other unit testing tools, CUT doesn't strive to be an SUnit clone. It automates a lot of the drudge work often encountered when using other unit testing packages for the C family of programming languages. CUT may also be used to unit-test assembly language software in some circumstances.
DBG is a PHP debugger and profiler. It makes it much easier to discover the origins of problems and bugs in PHP scripts. It's equipped with the ability to backtrace errors. It shows local and global variables as well as parameters which have been passed to all nested function calls at any point of execution. Among other things, it allows you to execute scripts in a step-by-step manner, set breakpoints (including conditional ones), evaluate expressions, and watch variables. The profiler allows you to find bottlenecks in PHP code at the functions level as well as the modules level and even the source lines level.
cspot is a semantic annotator designed only for the C programming language. It is quite similar to cscope, but some more functionality. It can be used to find the declarations, definitions, and usages of functions, variables, macros, typedefs, and structs. It can also find visible identifiers at some position in the source, functions called by a function, global variables used by a function, usages of local variable declarations, unused global variables, unused function definitions, and more. Because it uses sparse, cspot knows more about semantics than cscope.
pretrace is a preload library that allows specified (dynamically linked) applications to always be executed under a debugging environment. pretrace allows you to specify the percentage of invocations which will be traced, to help you "keep an eye" on applications without bringing the machine to its knees.
The C Code Analyzer (CCA) is a static analysis tool for detecting potential security problems in C source code. It's fully automatic; no code annotations or the like are required. It features an automatic user input tracer, potential buffer overflow detection, and more. An eclipse frontend plugin is included.