I already posted about image magick before but since this time I actually needed to use it, I found the "for" statement to work better than find.

$ for i in *.jpg; do echo "$i"; convert "$i" -resize 600x "$i"; done

Edited:

$ for i in *.JPG; do echo -e "$i...\c"; convert "$i" -resize 600x "$i"; echo done; done