Howto change the extension of multiple files

This happens to me when I'm importing photographs, I end up with files called .JPG or .jpeg and I prefer .jpg.

for file in *.JPG
do
  mv $file `basename $file .JPG`.jpg
done

The command rename does this same thing nicely, but knowing the for loop way can be more useful sometimes...and if you didn't know about rename, then I guess that would be useful too.
rename .JPG .jpg *.JPG