I would highly recommend a three tier backup strategy.

The first two tiers should be disk based; preferably on a mirrored RAID drive, or RAID 5 set, but not necessarily.

Tier one consists of regular incremental data backups of your critical user data, personal files etc... Basically anything that changes frequently and needs to be recovered.

The second tier is a periodic full image of each computer, also stored on disk; and also a baseline image for each comptuer, containing nothing but the completely bare and clean image of your OS, applications, and settings (i.e. no variable or optional data).

I recommend doing this at least once a month.

The third tier consists of writing one copy of the baseline image, and one full copy of all your user data to removable media; and if possible storing it offsite.

I recommend updating the userdata disk once every thre months or so.

In terms of technologies; if you have a spare machine and some very basic knowledge of Linux, a couple hundred bucks for hard drives should give you more than enough space to build a dedicated backup server. There are livecd distributions setup to do just that.

If you include two seperate sets of disks you can also make it your primary home file server.

Include a dual layer DVD burner in there, and you've got your removable media as well.

You could also buy one of the pre-built systems from Maxtor or Lacie.