Installing RMagick on Mac OS X with MacPorts
The install script can't find Magick-config in your path. Did you use a non-standard install location when you installed ImageMagick through MacPorts? Usually it goes into /opt/local/bin/
You can see where MacPorts put your Magick-config by running:
port contents ImageMagick
If you find it listed there, then make sure that the directory is included in your PATH and rerun the rmagick install.