Though it does involve trusting a third party, I signed up for a Mozy account. The initial backup is painfully slow (hint: concentrate on the vital files first, then add the less important files to the backup set). As I type, I'm still in the initial backup stage, but I'm already quite pleased with how it works. You install a programme, tell it what you want backing up, and it gradually squirrels it away for you. You can carry on using your computer and let it do its thing.
In the application you can say exactly what you want backing up. You get 2gig for free, and unlimited storage for roughly 1 US dollar per week, paying for two years up front (I paid with a UK visa card).
It's not a fast backup, but it is off-site, i.e. if I'm robbed, that data isn't gone. It's also automatic, so once my first backup is done it'll sit and add new files as needed - and as it only sends the changes, these will be done much faster.
I still want a hard drive backup for convenience. I've just bought a Seagate external drive (which has been nothing but problems - I took it back to the shop and I'm now on drive two, and that doesn't work either.... if Seagate support don't get their finger out, I'll be seeking a refund).
Whilst the hard drive (when it works!) is faster, if robbed or some other disaster strikes, it's likely to get taken out at the same time as the computer. For reassurance that the important, irreplaceable and difficult to replace stuff is safe - the Mozy account looks ideal (in a world where there isn't the nice off-the-shelf compromise between hard drive and off-site I described in my last post).
The Mozy solution does involve trusting the third party. I can set an encryption key (which I must know to recover data), or use a default key. Even with my own key I know I'm trusting there isn't a back door, however to break this trust is more than their business is worth and my data isn't that interesting to a random person, so it's fine by me. If this were a concern I could run a script to automatically encrypt and compress my data locally, and then store that file on mozy.
As I say, I'm still in the slow initial backup phase, but I've already done a test restore via the web onto another machine and it was totally fine. Looks good to me.
In short, it's automated off-site backup of the most important files, at a cost which is comparable to an external hard drive every few years.
I hope to never have to rely on it - but recent problems with the computer mean that I'll feel a lot better once my initial backup is done.