Like the above post says, look for Mac the Ripper. It decrypts DVDs directly to your hard drive. You can then use an app like Popcorn to compress it further to fit onto a 4.7GB DVD, or if you purchase a DVD Burner that supports Dual-Layer discs, then you can likely fit the entire movie on that.
If you are looking for something more portable, you can use an app such as
Handbrake to convert your movies from DVD into a MPEG4 movie, which will make it about 700MB in size, but you lose quality (though it may be good enough for you) and the ability to use chapters and subtitles, etc.