I know Pamperchu started a thread like this a few years ago but I wanted to post a similar one so new users like me (or people who didn't catch his old thread back in 2012) could provide their input.
For me, I have 2 80GB drives in my mac which are backed up by using Carbon Copy Cloner (PowerPC) onto 2 partitions on a 1TB External drive.
I also have photos and videos backed up on DVD's and CD's and even (brace yourself)... VHS!
Yeah, it's pretty rad.
So, what format do you use? (If any)