Dave-Looking Outwards-Shields
1. CMUcam
https://www.sparkfun.com/products/10032
Made by CMU, this can be used to collect visual information from the surrounding, allowing the Arduino to detect changes in light, color, or motion.
2. VoiceBox Shield
https://www.sparkfun.com/products/10661
With a sound synthesizer, we can generate voice, thus allowing the Arduino to speak. This can be very useful to communicate messages en masse.
3. TFT Shield
https://www.adafruit.com/products/802
We can display images via this shield, and with some modifications we can display text also. This allows for a wide range of outputs.