After much trial and error, I've gone with the robust solution that's never failed me:

robocopy.exe /MIR <source> <target>

Create a scheduled task, set your external drive as the target, and forget. robocopy.exe is a built-in utility for Windows 7 and can be freely downloaded for via the resource pack. Also consider an offsite solution such as Windows Live Mesh for the free 5GB to create offsite backups of the most important folders. Never know when a catastrophic event (theft, fire) can take out your backups.

Unless I'm misreading this, it only mirrors your drive with no history. That's a poor approach - if your drive starts packing in you're likely to backup a fair amount of corruption before you realize what's going on.

Ditto if you screw up - you have to catch it before the next backup otherwise you're boned.

Been using the Freeware version Syncback for over 5 years now. Highly recommended: (http://www.2brightsparks.com/syncback/index.html)

Another happy SyncBack user here.

Bvckup [1] might be of some interest. I've been using it for a couple of years and it's a setup-and-forget kind of software. It's a bit dated, but a newer version is in works.

[1] http://bvckup.com

Why not use Windows itself? It has a decent backup system.

Alternatively, for syncing and not real backuping (no timestamped snapshots, for example), I've used FreeFileSync[1] successfully in the past.

[1]: http://sourceforge.net/projects/freefilesync/

FreeFileSync is great if you just want to keep an up-to-date copy of everything and you don't need multiple incremental backups. It compares file size and timestamps and only copies files that have changed. You can save batch jobs as a file and click on it whenever you want to sync. You can even make the batch job autorun when you connect your external hard drive.

Throw TrueCrypt into the mix, and you've got a pretty good and secure backup.

Have you tried the built in Win7 backup system? It's gotten considerably better over the years. Acronis True Image is a commercial solution (~$40) that may be a bit overkill for your needs but it does a good job and is feature rich.

If that's all you want, I'm sure you can find a Windows equivalent to dd to run every day. Do a direct bit copy, and then your external disk will always be in sync with your internal disk.

That's a terrible idea. Backing up with disk images will take a long time, erase your previous backup at the start, and not prevent against filesystem corruption.

Should Checkout CloudPull for the mac for backing up google services. Yes, everyone should backup gmail. If you get hacked and all your email deleted, googles backups won't do you any good.

Arq is a good backup-to-cloud service if you're conscious of where your data goes(S3) and who has the keys(Only you).

They're both indie programmers out of Boston too, which may be some of my bias, but check'm out!

Dropbox for pc/mobile and Jungledisk for servers.

Dropbox is for syncing, not backup. There is a difference, and people don't care about the difference until they run into problems.

Dropbox doesn't delete your files when you delete them from dropbox. You can always restore them later, I have used that feature countless of times. So Dropbox can act like a backup, I still use JungleDisk to backup my whole dropbox just to be safe.

Depends on what you mean by "backup".

Backup to me (and most others that I've talked to) means "I can restore all my data, my entire hard drive, and be back to where I was yesterday, so if I screw up my kernel tonight, I can just use the backup to revert to my pre-kernel hacking spree".

(to an average joe, it means the same thing, but not as much detail)

By default Dropbox keeps 30 days of old versions. You can pay extra to bump that up to "forever".