There is a nice little tool available in the OS X Terminal to batch resize images called sips.
sips -Z 1024 *.jpg
This command will resize all images ending on .jpg in the current folder to a maximum size of 1024 pixels by maintaining the aspect ration. That means that landscape images will have a width of 1024 pixels and portrait images will have a height of 1024 pixels.
ATTENTION: Note that this command will replace your original images. Use the additional
--out flag to specify an optional output directory.