What do you use for backup today?

Over the past few years the capacity of disk drives (and the amount of
space typically used on them) has greatly increased, and now it is
getting more and more difficult to figure out how to back up these
drives.

What type of hardware (and software) do you use on your systems for
backup?

Up to now, I've used HP DDS tape drives (DAT drives) for backup. But
DDS2 is limited to 4 GB, and DDS3 is limited to 24 GB, and that's
getting to be to small to hold even one backup on a single tape (or
even on several tapes in some cases).

So, what else is there? These DAT drives already cost me a fortune in
the good old days, and today they cost nearly as much as the rest of
the computer, when I can find them ... and even DDS4 is still limited
to 40 GB. DLT drives are several times more expensive at the cheap
end, although they do have capacity to hold an entire drive of data.

Are there other practical alternatives? What about external USB
drives, can that work? Old stuff like Zip drives and so on is
history, as it has even less capacity than tape. Archiving to CD or
DVD is also too low in capacity. It's getting to the point that the
only affordable option seems to be some sort of disk-to-disk copy (or
RAID for those who can afford it), but it would be nice to have
removable media that could be put in a safe place.

So what is everyone else building into their new machines for backup?
And do you just use standard backup tools like ntbackup on Windows or
dump on UNIX, or do you use special software purchased separately?