Depends on what you are trying to do. Couple of (no longer supported or current, but still quite functional) programs out there which would work for most of your needs would be DVDFab and DVDShrink. However, while they are free, they can still be a pain in the rear. I would suggest going to Slysoft's page and checking out their suite of programs. Yes, it costs a little bit, the the total lack of headaches and the constant updating of their software to keep on top of the latest schemes makes it very much worth it. I suggest them for making all of your legitimately-owned and legal backups.
DVDShrink and Decrypter is still the ones I have used. DVDShrink is actually pretty easy if you are doing a simple conversion or "backup."
Well, you can get plenty of that software out there for free, but just try and use it. After you spend a good 30 minutes waiting for it to analyze files and what-not, THEN it will tell you that it cannot burn the digital audio stream without you having to pay some $, whereupon it will go ahead and burn you a nice coaster of video with no audio. If you want full-function versions of their software, especially for DVD's, you're not getting that free. The big problem with things like Decrypter and Fab and Shrink is the fact that there is definitely a big difference not only between the relative quality of burners out there, but also the fact that the ability of home dvd players to handle these kinds of discs will vary from brand to brand and even from player to player within the same brand sometimes. And then you add in mostly unsupported and non-updated programs like those three above, and well, you're going to be wasting a lot of time and making a lot of coasters. That's why I love Slysoft's stuff so much. I figure the relatively small initial outlay that it cost me to buy the package is more than made up in the saved time, far fewer ruined and wasted discs, and a much higher compatibility rate with the various home players in the house. If you want to be serious about making quality backups, then you also need to get a seriously good quality burner. They are generally not much more than the no-name or off-name brands. Look for a Pioneer or a Plextor, you can't go wrong there. I used to use a cheap Emprex dvd burner, and I got a lot of coasters, and disc failures. I thought I must have bought a bad batch of discs, but as I learned more about it, I ditched the Emprex and bought a Pioneer, and that did away with 90% of the bombs, AND greatly improved the compatibility when reading in all the various players too.
