I suppose you could write a C backend for LLVM, then you could translate pretty much anything down to C, but the deeper question would be "why?" The reason that there aren't any tools that do this today is that if you are going to compile down to C, why not go all the way and target some intermediate machine code language instead? (For example, LLVM or the JVM)
Now in the older days, the idea of compiling down to C was a bit more defensible, since there was a lack of decent vm languages, but today there are not too many good reasons to do it. That said, you can still find plenty of projects around which take certain interpreted languages and try to compile them down to C/C++. For example, here is a python to C++ compiler:
http://shed-skin.blogspot.com/
