You can use jpegoptim which will losslessly optimize jpeg files by default. The --strip-all option strips all extra embedded info. You can also specify a lossy mode with the --max switch which is useful when you have images saved with a very high quality setting, which is not necessary for eg. web content.
You get similar optimization as with jpegtran (see answer by OutOfMemory) but jpegoptim can't save to progressive jpegs.
