Commercially made blu ray movies tend to be anywhere from 18 to 45gb in size, slightly less if you are talking about movie only and no extras included. There is a program called BD-Rebuilder which can compress them to fit a single layer dvd, you just set output as a BD-5.
BD-Rebuilder is free to use. It needs three other free programs installed in order to work, but there are direct download links to them at the BD-Rebuilder download page: http://forum.doom9.org/showthread.php?t=143716
Read that first post carefully.
The output will be blu ray video that is AVCHD compliant, which helps compatibility with stand alone blu ray players, but you should be aware that not all blu ray players can handle these disks. They should play on a computer that has blu ray player software without issues.
Compressing HD material requires a fast computer, one with a multiple core processor would help immensely. But even so, it will take a long time to compress this type of video.