Some useful tutorials and projects:
Sound
- Using a USB Audio Device With a Raspberry Pi
- Raspberry Pi Internet Radio Player
- Raspberry Pi Internet Radio
Display
- Motion sensitive photo frames
- Build Blog: Digital Photo Frame Powered By 500px, Raspberry Pi, and Ruby That Compliments Your Day
Digital Signage
PiCamera
- Raspberry Pi remote webcam
- Using standard USB webcam
- stream from the Raspberry Pi Camera board
- Time-lapse Photography with the Raspberry Pi Camera
- How to install or upgrade UV4L on Raspbian Wheezy & Raspbian Jessie for Raspberry Pi
Motion sensing
- Make a motion-sensing camera with the Raspberry Pi
- Parent Detector / Learning Pi
- Raspberry Pi GPIO Sensing: Motion Detection
Misc
- PrivateEyePi – Home Automation and Monitoring Projects for Raspberry Pi
- CarSpberry 2 – “CatSpberry 2″ is a toy forklift controlled by raspberry pi
- Raspberry Pi, Xbox 360 Controller, Python