Online Documentation: http://www.imagemagick.org/script/command-line-tools.php
How to downsize a whole directory of graphics
How to convert a color graphic (e.g. .pdf or .ps created by Sweave) to grayscale and still have it be publication quality
Tip #1: Use "convert -density" to convert a vector graphic to a raster graphic at supplied density, say 300dpi.
Tip #2: To create rotated text: convert -rotate -45 label:"FOO BAR" foo_bar.gif