MAME is a multi-purpose emulation framework
JUCE is an open-source cross-platform C++ application framework
A text-based widget toolkit
A cross-platform file change monitor with multiple backends
Open source framework simplifying the creation of C++ applications
A multimedia framework based on Qt and FFmpeg
Real-Time Event Frameworks based on active objects & state machines
MuldeR's Utilities for Qt
C++ Statistical ToolKit
C++ Frontend for the RenderMan Interface
A simple 3D framework in C++
Cross-platform C++ library for use as a default application framework.
Development framework based on message driven provided
A framework in which the system is defined by a xml file
polyglot language framework to analyze genetic data
x86 Multi-Core Microprocessor and assembler simulator written in C++
Keystone assembler framework: Core (Arm, Arm64, Hexagon, Mips, etc.)
Now maintained at https://code.google.com/p/lpi/