BD Rebuilder is free to use and will compress Blu-ray movies to fit 25gb discs. You can make movie only copies, or you can compress the entire thing, menus, extras and all.
You will need to decrypt the movies before using BD Rebuilder.
There is a link to my guide to the program down below, in my signature.
Handbrake is for converting various types of video, including Blu-ray, to MP4 or MKV files.