Article - A list of common CMake antipatterns (from 2013 but still relevant).
Package Management
ruslo/hunter - Cross-platform package manager for C++ (based on CMake ExternalProject). BSD2
pfultz2/cget - CMake package retrieval. This can be used to download and install CMake packages. BOOST
iauns/cpm - A C++ Package Manager based on CMake and Git. MIT
conan-io/conan - Conan C++ Package Manager, implemented in Python and has a CMake integration backend. MIT
Modules
rpavlik/cmake-modules - A collection of CMake modules. There are a number of find modules, especially for virtual reality and physical simulation, some utility modules, and some patches or workarounds for CMake itself. BOOST
bilke/cmake-modules - This is a collection of additional CMake modules. Most of them are from Ryan Pavlik. BOOST
These provide a wide range of functionality - from dealing with compiler flags to using tools. Some also contain modules.
sakra/cotire - Cotire (compile time reducer) is a CMake module that speeds up the build process of CMake based build systems by fully automating techniques as precompiled headers and unity builds for C and C++. MIT
onqtam/ucm - For managing compiler/linker flags, collecting sources, precompiled headers, unity builds and others. MIT
toeb/cmakepp - An Enhancement Suite for the CMake Build System. MIT
ruslo/sugar - CMake tools and examples: collecting source files, warnings suppression, etc. BSD2
Crascit/DownloadProject - CMake module for downloading an external project's source at configure time. MIT
ruslo/weather - Example of using Hunter cross-platform package manager for CMake to build application which use Boost, CppNetlib.URI, GTest, JSON Spirit. Platforms: Windows (Visual Studio), Linux, Mac OS X + iOS. BSD2
OutOfOrder/CMakeTemplates - A set of initial CMake templates that I use for every game port I work on. [NO LICENSE]
fletcher/c-template - Boilerplate to set up a c project, include CuTest, cmake build setup. MIT
duckie/cpp_project_template - A simple template to start quickly a C++ project managed by CMake. [NO LICENSE]
Other
coderefinery/autocmake - Using a autocmake.yml file Autocmake composes CMake building blocks into a CMake project and generates CMakeLists.txt as well as a setup script, which serves as a front-end to CMakeLists.txt. BSD3
kmorel/UseLATEX - A collection of CMake macros to simplify building LaTeX files. BSD3