I’m a huge fan of my Time Capsule. Once an hour, both my MacBook Pro and Air machines are backed-up automatically via wifi without me having to do a thing. As a wise friend once observed, the only 100 percent reliable backup system is one where you don’t have to do a thing – not even plug in a drive.
But there’s no denying that at $299 for the 2TB model or $399 for the 3TB model, the Time Capsule isn’t cheap. You can buy a 2TB external hard drive for well under $100 or a 3TB one for slightly more. You’d normally need a more expensive NAS system to make it work via wifi, but Remy van Elst has created an instructible enabling you to do it with nothing more than a $35 Raspberry Pi.
You’ll need to be comfortable with command lines, and it will take you a little time to get it all configured, but at the end of it all you’ll have a working Time Capsule – that looks to OS X just like the real thing – for somewhere around $120.