Microsoft BitLocker - BitLocker is a full disk encryption feature included with Windows Vista and later.
madCodeHook - "madCodeHook" offers everything you need to hook code (mostly APIs).
Paubox - Paubox provides HIPAA compliant email encryption without the hassle of extra steps.
Deviare API Hook - Deviare is a professional open source hooking engine for instrumenting arbitrary Win32 functions, COM objects, and functions which symbols are located in program databases (PDBs).
OpenSSH - OpenSSH is a free version of the SSH connectivity tools that technical users rely on.
Microsoft Research Detours - Detours is a software package for re-routing Win32 APIs underneath applications.