Run Command Line Script from Finder's contextual menu
If you're using Snow Leopard, you can create a Service, and it'll show up in a submenu of the contextual menu (as well as in the Services submenu of the Finder menu).  To do this:


Run /Applications/Automator.app
Choose the Service template
Set the Service Receives Selected pop-up (above the workflow column on the right) to "Files and Folders"
Find the Run Shell Script action in the second column (the search field at the top can help), and drag it to the workflow column
Set the action's Pass input: pop-up to "as arguments"
In the template script that appears, replace echo "$f" with exiftool -all= -overwrite_original "$f" -- the script should now look like this:

for f in "$@"
do
    exiftool -all= -overwrite_original "$f"
done

Save the Service with some descriptive name