Code.
.org
This is an online code browser that can be used to read the source code of many free software projects. It is created using the Woboq Code Browser generator.
It focuses on improving the code navigation with proper semantic highlighting and tooltips. Read more about it in our blog post or take the feature tour.
The source code of this code browser can be browsed or can be cloned from github. Please report bugs or suggestions to the bug tracker.
Qt 5 and KDE Frameworks 5
Sources of Qt5. http://qt-project.org. Including Qt Creator.
And sources of KDE Frameworks 5 http://kde.org.
Contains 
QtWebkit
and Chromium as part of QtWebEngine.
KDE 4 and Qt 4
Many of the KDE repositories. http://kde.org.
Contains also 
Qt 4 and
Quassel (quassel-irc.org).
Linux
The sources of the linux kernel. (kernel.org)
glibc
The GNU C Library. (www.gnu.org/software/libc)
LLVM
The LLVM (Low Level Virtual Machine) compiler infrastructure. (llvm.org). Including Clang (the C/C++ compiler)
GCC
The GNU Compiler Collection. (gcc.gnu.org).
Boost
The Boost C++ libraries. (boost.org). 
LibreOffice
The LibreOffice suite. (libreoffice.org). 
All code on code.woboq.org was generated on linux x86_64.
Inspired by KDevelop
.