Of course, you can make your own choices in all of the above tech. I was just providing a list for the sake of examples. The point is, each of these things is the core value of these other businesses and they do them better than you will be able to. It's absolutely worth the small fees they charge to keep you focused on your core product.
Every night the NAS compresses and encrypts the whole archive and pushes a copy to a VPS at the provider site. This way I am sure I have a relatively recent off-site copy, and it is secured enough, so that even the VPS provider is unable to read it.
I use GoodSync for synchronizing my documents folder with the NAS. Also NAS is reachable from the public internet over HTTPS, and I can synchronize my files when I'm at the customer site.
Also I use another VPS (extremely cheap one from http://www.buildyourvps.com/ -- a bit slow, but fine for these needs) as my Git storage. I use Gitolite to organize my Git repositories, and basically create a new repository for every set of scripts or configuration files that I do for my clients.
For public and open-source code, I use Github.
A third VPS is used as a virtual PBX where I organize hotline service for those of my customers which need support with an SLA. You can see some technical details in my blog (http://txlab.wordpress.com/tag/dvop-net/). Also an instance of RT: Request Tracker is running on it.