I use Time Machine to an external drive, but I'm rethinking that since I don't keep that drive powered up at all times. I have an array of internal drives (Mac Pro user), so I may create a partition on one of those for frequent Time Machine backups. I haven't had to recover anything from TM backups yet, but I like the idea of being able to easily roll back to an earlier state if needed.
I use Prosoft Data Backup (which came bundled with the external drives from OWC), to back up my non-boot internal drives to external drives on a daily basis.
SuperDuper! (similar to Carbon Copy Cloner) is for making daily clones and backups of my boot drive, so I can recover in case of catastrophic failure. (Never happened yet in 7 years of using Macs, but of course the first day I let down my guard is when disaster will strike!)
A couple of things on my to-do list: 1) make a bootable disc with the Lion OS on it and 2) update my emergency bootable thumb drive (haven't done this since going to Lion). I also need to get back to storing backups of key files off site -- I was keeping up with that at one point but let it slide. I'm too paranoid to use cloud-based backups for most files, so in case of fire, theft, or other major home disaster, I need to get a good off-site backup strategy in place and keep up with it on a regular basis.
All this stuff is for personal and hobby use (so far), but it really would be terrible to lose the material I have on this machine and backup drives -- so I take this seriously.
Thanks for the topic, CA! This is a reminder to me to get my own digital house in order.