I needed to resize several hundred jpg so I did a little googling and came across this freebie. Photoresizer.
There are probably others as well but this one was simple to use and it worked so well I figured I'd give it a plug.
http://graphicssoft.about.com/gi/dynamic/offsite.htm?zi=1/XJ&sdn=graphicssoft&zu=http%3A%2F%2Fwww.rw-designer.com%2Fpicture-resize