Creating a secure backup is important. Not only should your photos be accessible, but you should also be able to recover them in the event of a computer crash, natural disaster or theft without it being a difficult or financially prohibitive process.
To accomplish this, you're going to want to backup and archive in several ways. An external hard drive should be part of your backup plan. However, keep in mind that research shows external hard drives have a limited shelf life of five years or so. If you keep your external hooked up to your computer for backups that happen on a regular basis and your computer is stolen...the thief is probably going to take your external hard drive too. That happened to a friend of mine. Her computer was stolen right out of her house, with the external hard drive attached. She lost a couple years worth of pictures.
You may also want to consider Picture Keeper. Picture Keeper has built in software that searches for and saves your photos in their original file structure. It's easy to use, because it's programmed to find your photos for you. The next time you plug it back in, it'll find the new photos, as well as those that have been edited.You'll also want to take advantage of cloud storage options. One of my favorites for photos is Linea for its photosharing and beautiful viewing capabilities, but I also use Dropbox on a regular basis. When considering a cloud storage service, you may want to consider privacy and security, and you should make sure you can retrieve your images and export them back to your computer in the same resolution you uploaded them at. You also want to make sure the site stores your images on more than one server.
Another backup option is copying your photos onto archival quality CDs or DVDs and storing them away from your home. Fires and natural disasters, while not regular occurrences, can happen. However, remember if you store on CDs or DVDs, you will need to re-record at some point, as technology changes. 
And last but certainly not least, the printed photo is your best backup! Printed photos are not vulnerable to technological obsolescence and can last hundreds of years if stored properly!
If you need help with coming up with a backup plan for your photos, the professionals at the Association of Personal Photo Organizers can help. Check out the APPO site for a personal photo organizer in your area.Check out the World Backup Day site for more backup solutions!
