Does anyone know where I could download a good DVD to Mp4 ripper online for free? Please help if you can :)

I have so many good DVD box sets I want to put on my iPod and I have loads of memory left on my iPod :)
I've downloaded a few different rippers I've found but the finished product has a watermark or else you have to pay for the product. So I was wondering if anyone uses a good one and if they could link me so I could download it.
Thanks xx