ANONYMOUS or you can type from terminal:
defaults write com.apple.screencapture type pdf
This changes the default to PDF; you can also use PNG, GIF, and JPG (Version 0.2)
ANONYMOUS Follow this link, it takes you to English:
http://babelfish.altavista.com/babelfish/trurl_pagecontent?lp=fr_en&url=http%3A%2F%2Fwww.clampin.com%2FChanger-le-type-de-capture-d-ecran (Version 0.2)
ANONYMOUS And it works with Panther. (Version 0.2)
EUG It does what it's advertised to do, and it's free. Can't argue with that. :) (Version 0.1)