There are a number of compilers that can be used for D or under active development.
The Digital Mars D Compiler ( DMD) is the official compiler. Supports the x86 architecture and several operating systems.
The LLVM D Compiler (LDC) is a port of the DMD frontend using the LLVM backend.
The GNU D Compiler ( GDC) is the DMD frontend using the GCC backend.
The D.NET Compiler is still in need of a lot of work before it is practical to use on any project.
The D DMD compiler ( DDMD) is a port of the DMD compiler to the D programming language. It is intended to be a "drop-in replacement for DMD." Currently not usable for compiling D programs.
dil is being developed as a D frontend written in D. It is not able to be used for compiling, but is under slow development.