exabyte is what i use. depending on your needs, you should evaluate whether or not tapes are really best for you. is this for an offsite backup? if your just trying to create some redundancy, i would just use hard drives and create mirror sets. if you already have a computer you can do this with, two forty gig drives are a lot cheaper than backup tapes.
my computer is so fast, it completes an endless loop in less than 4 seconds!