Writing a FindXXX.cmake module that works with shared libraries is relatively easy. You need only find the interface libraries and the system will take care of resolving dependencies when the executable is run. With static libraries, the linker must be provided with the entire dependency graph. Determining the dependency graph is project-specific, but common methods are wrapper compilers, Makefile systems, and pkg-config. All of these provide a link line which includes all dependencies. However, CMake does not accept link lines directly. A hack is for the CMake module to parse the link line itself. To be truly portable, the semantics of the underlying linker must be preserved. Normally this means that each library pathh is added to a stack and each library is searched in this stack and then in system directories. Every module distributed with CMake that attempts to parse link lines gets this wrong as of 2.6.3rc1 when Multiple versions of libraries are present. Most FindXXX modules make no attempt to resolve dependencies, hence require manual intervention when shared libraries are not available.
The ResolveCompilerPaths module provides macros RESOLVE_LIBRARIES and RESOLVE_INCLUDES which do better, but still are not perfect. Example FindXXX modules which uses these macros are FindPETSc.cmake and FindiMesh.cmake.
There is no way to ask FIND_LIBRARY to only find static libraries. See this bug report.