Valgrind - Valgrind is an instrumentation framework for building dynamic analysis tools.
API Monitor - API Monitor is a software that monitors and displays API calls made by applications and services. Its a powerful tool for seeing how Windows and other applications work or tracking down problems that you have in your own applications
strace - Trace system calls and signals. A diagnostic, debugging and instructional userspace utility.
EasyHook - The reinvention of Windows API Hooking
Microsoft Research Detours - Detours is a software package for re-routing Win32 APIs underneath applications.
JTracer - C++ exception (and generic) stack trace debug suite