#Step 1: Download the ImageMagick files 
http://www.imagemagick.org/download/binaries/ImageMagick-universal-apple-darwin9.6.0.tar.gz

#Step 2: Unzip the files which should give you a directory like /ImageMagick-6.x.y

#Step 3: Open up the Application Terminal and type "open /usr/local/"

#Step 4: Move /ImageMagick-6.x.y into /usr/local/ (This may require you to enter a password)

#Step 5: Type "mate ~/.bash_profile" into Terminal. The application TextMate will open a blank page.  If you already have an existing file with the same name, TextMate will open the file.

#Step 6: Paste this code
export MAGICK_HOME="/usr/local/ImageMagick-6.4.8"
export PATH="$MAGICK_HOME/bin:$PATH"
export DYLD_LIBRARY_PATH="$MAGICK_HOME/lib"

#Step 7: Quit Terminal and re-open it

#Step 8: Try these commands in Terminal to see if everything works

"convert logo: /Users/ttrojan/image_file.gif"
"identify /Users/ttrojan/image_file.gif"
"display /Users/ttrojan/image_file.gif"

It seems that a lot of people are afraid of installing ImageMagick because they've either heard a ton of horror stories or aren't used to installing things that aren't pre-packaged (i.e. DMG).  Well the truth is that it's pretty easy.  Here's how I did it using OS X Leopard and Textmate.

Installing Image Magick on OSX

Bash