Batch resize/Compress all images in a folder.

Make a new file (not as root):
Run In Terminal
#gedit ~/.gnome2/nautilus-scripts/batch640x480

and then Add
#!/bin/sh 
# Use this script to batch resize all images in a folder. 
# First open the folder and then use the script.  
for file in `ls -l` 
do 
name=`echo $file | cut -f1 -d.`
convert -geometry 680x500 -quality 65 $file ${name}_680x500.jpg
done


Save this file and make this file executable:
#chmod +x ~/.gnome2/nautilus-scripts/batch640x480
Go to the folder you'd like to resize. Then rightclick and find the 'batch640x480' script.
I use this script for resizing large amounts of photo's for a website