Started by one of our readers more than a week ago was a compiler deathmatch for comparing the performance of GCC, LLVM Clang, PCC (the Portable C Compiler), TCC (Tiny C Compiler), and Intel's C Compiler under Arch Linux. This user did not stop there with compiling these different x86_64 code compilers, but he also went on to look at the compiler performance with different compiler flags, among other options. The results are definitely worth looking at and here are some more.
If you want to test the speed of the resulting binaries, PLEASE test also what the compiler is able to do and not only what it does in default configuration. Please include maximum optimization in the benchmarks.
Michael, unless you tell the compiler to optimise, it won't optimise. These results are completely useless. It's like testing how fast different graphics cards render with the Mesa software rasteriser.
The interesting results would be to see what effect different optimisation levels (-O2, -O3, -Os, plus compiler-specific features) have on the final executable. This will help individual developers and distro packagers to pick the best compiler options for specific programs. This would need about 5-6 different configurations per compiler and most of us don't have the time to do it at home, so we would be very grateful if you do a proper benchmark.