Services are a new edition to Mac OS X Snow Leopard and can make life super simple. One thing I'm always doing is converting video files into iPhone friendly format for watching on my daily commute. Now instead of having to open Handbrake and do this manually I can right click on a file and select 'Convert to m4v' using the following:
Service receives selected movie files in Finder
for f in "$@"
do
/usr/local/bin/HandBrakeCLI -i "$f" -o "$f.m4v" --preset="iPhone & iPod Touch"
done