Hopefully you are backing up your images and have a super tight workflow. You do… Right?? I may have posted about this before but it is worth revisiting. Hard drives fail. They fail all of the time. If you are using your hard drives for image storage, make sure you have redundant copies. I have had them fail in the past and it is unsettling, even if you have backups. (I also recommend off-site backups, whether you send DVD copies to your parents house, have an online service, etc..)
drobo has been on the scene for a while now, but they have an updated version that utilizes firewire 800. I have the older USB 2.0 editions but they are still fantastic. I have 2 drobos. One at home and One at the studio. I use another drive in between to transport data for backup. The drobos are so easy to use and set up. You can start with two drives and add up to two more. It manages the technical stuff for you so you do not have to think about it. Be forewarned though, that there is still risk of failure and one backup is not enough. OK, I am done ranting about backup.
**UPDATE** Just found this gem via the TWIP (this week in photography) podcast: Save $50 on a drobo!
You can get the drobo at many retailers including the drobo site. Here is a link to their video about the drobo.