Ideas:

• Geiger counter
• Japanese 1seg
• FM transmitter
• POWERFUL FM transmitter
• interface w/ arduino
• solar powered remote weather station
• use tablet/smartphone for game controller
• Connect something unusual via USB (learn the protocol, etc)

Wishlist:

https://www.adafruit.com/products/1567 https://www.adafruit.com/products/1940 https://www.adafruit.com/products/1766 https://www.adafruit.com/product/345 https://www.adafruit.com/products/342 https://www.adafruit.com/products/1733 https://www.adafruit.com/products/1713 https://www.adafruit.com/products/483 https://www.adafruit.com/products/924 https://www.adafruit.com/products/469

http://www.aliexpress.com/item/DIY-Sharp-PM2-5-Sensor-Dust-Sensor-GP2Y1010F-for-Raspberry-PI/1715331366.html http://www.aliexpress.com/item/MQ-3-Gas-Sensor-Module-alcohol-ethanol-detection-MQ3-for-Arduino-STM32/2041893899.html http://www.aliexpress.com/item/Raspberry-pi-PCduino-cubieboard-car-driver-module-with-opto-isolation-L298N/2042833556.html http://www.aliexpress.com/item/Smart-car-module-smart-car/1600979962.html http://www.aliexpress.com/item/Raspberry-pi-LSM303DLHC-module-6-axis-sensor-module-Test-acceleration-Balancer-Compass/2042796160.html http://www.aliexpress.com/item/Smoke-sensor-mq2-mq-2-full-set/1611248881.html http://www.aliexpress.com/item/I2C-BMP085-Digital-Barometric-Pressure-Sensor-board-Barometer-sensor-module-for-Ardunio-AVR-PIC-ARM-Raspberry/1628119256.html http://www.aliexpress.com/item/Raspberry-Pi-B-8x16-dot-matrix-module/2042919254.html