One of the most important things you can do with a computer is BACK UP YOUR STUFF!
I've had numerous hard drives fail and lost shit loads of stuff over the years, but still never get round to backing up properly. I then found GetDataBackForNTFS a neat little program that recovers even failed hard drives (so if a drive failed I wasn't too bothered). However I've had one drive that's lost all the files and I can't seem to get them back no matter what so a bit gutted.
In my attempts to recover the data I stumbled across Hiren's BootCD and found it had a few back up tools on it. One of which is called Roadkils Unstoppable Copier. It seems really good as like the name suggest - not like windows when you try and copy a folder with another folder in it etc you just get nag screens and have to be sat with the machine (not viable when backing up a 3TB drive). So this program has settings to only copy the new files etc...
I've experimented with AlwaySync in the past, but found it takes too long to scan the drive. It's good thogh as it will get rid of files you've deleted from the source folder.