DVD2OneX worked well for me for compressing DVDs and extracting certain sections from the contents. However it requires another tool to get past the copy protection tools and I forget the name of it, though I know it was free... look around.
Also, just so you know. OS X will let you create a disk image from a DVD and save it to your hard drive. This takes about 7GB of storage (though I haven't tried making a compressed disk image from one). Nice for storing full DVDs on your hard drive if you don't want to listen to your SuperDrive spinning the whole time... especially on a laptop.