If you don’t need to access your backed-up files remotely, buy an external hard drive, hook it up to your PC, and set it to back up automatically.
If you want to get fancy, buy an NAS. NAS stands for “network-attached storage.” It’s essentially a storage device with access to the Internet. In addition to accessing your backed-up files from anywhere, many NAS units come with additional features that you’d never get with Carbonite or any of the other subscription services. I use mine to stream music files to my A/V receiver.
Heck, these days you can even create your own cloud with an external hard drive so that you can access your data remotely from an HDD in your own home.