If you have upgraded to Xcode 4.x and miss the possibility to create C/C++ implementation (.c or .cpp) and header (.h) files in one step as it used to be possible in Xcode 3.x, download these Xcode file template (for C and for C++), and place the expanded .xctemplate directories into your /Developer/Library/Xcode/Templates/File Templates/C and C++ directory.

That’s it. The template will show up as additional options when creating a C/C++ file. You don’t even have to restart Xcode.