While computer powered personal assistants haven't really come into their own yet, that doesn't mean they're not useful. The Raspberry Pi happens to work great as an assistant, and Instructables user janw shows off how to convert an old intercom system to work with the Pi as a voice-controlled device.
The main part of the system here is the Raspberry Pi and the old intercom system, but it also uses a Wi-Fi adaptor, a soundcard, a small amp, and a few other cheap parts. The end result is a push button system where you can ask the Pi anything and it responds. It's a bit slow on the draw sometimes, but it's still a cool little system. Head over to Instructables for the guide to make it for yourself.
Raspberri Personal Assistant [Instructables]