Keeping files on a half dozen different computers scattered around the house doesn't make a lot of sense. For many homes (and small offices), it's a better idea to centralize things on a network-attached storage device, or NAS.
Up to 4 terabytes of easily accessible storage. Basic setup takes less than five minutes; ships preconfigured with most-commonly used settings. Default RAID 1 design means data is secure right out of the box. Small and unobtrusive.
Management console could be (a lot) friendlier, especially for novices. No wireless. )
NAS devices aren't known for their simplicity, but Seagate's BlackArmor is about as easy as they come. Preconfigured with the most common settings (like mirrored hard drives, to ensure that the data stored on the drive is always backed up), it can be plugged into your router and await software installation — then you're on your way. The BlackArmor can be used as standard networked storage by up to 20 connected PCs, or you can get fancy and use it to serve iTunes music with little more than the check of a box in software. Alternately, you can install software on client PCs to automatically back up files to the BlackArmor in real time.
Dealing with BlackArmor's in-depth management console is kind of like getting a doctorate degree in particle physics, but most users won't ever have to delve into it. Small and compact, it easily hides out of sight.