Sensors

Temperature

 * Some microcontrollers, such as the Atmel ATtiny, include an internal temperature sensor accurate to +-10 Celcius)


 * "1-wire" temperature sensor accurate to +-0.5 Celcius
 * software to make nice graphs from a bunch of temperature sensors on a "1-wire network"
 * nice waterproof packaging
 * pretty pictures of the actual sensor (plus wires and connectors)
 * DS18S20: 1-Wire Digital Thermometer (manufacturer's data sheet)


 * wireless temperature sensor accurate to ??? Celcius

Humidity

 * Sensirion digital humidity sensor

Atmospheric pressure

 * Intersema pressure sensors

Light

 * photodiode

Touch

 * touch sensor
 * http://capsense.com/
 * Cypress "CapSense" can be used for "buttons" and "sliders"

Tilt

 * The Fredericks Company tilt sensors
 * Spectron tilt sensors

Acceleration (Accelerometers)

 * Analog Devices iMEMS® accelerometers
 * Freescale semiconductor MEMS accelerometers

Angular Rate (Gyroscopes)

 * Analog Devices iMEMS® gyroscopes
 * InvenSense dual-axis gyroscopes
 * Murata "GYROSTAR" gyroscopes

6 degrees of freedom inertial sensors (3 accelerometers + 3 gyroscopes)

 * Analog Devices ADIS16350 Tri Axis Inertial Sensor

Magnetometers (Compass)

 * PNI Corporation Magnetic Sensors (including 3-axis magnetic field sensing module)

Global Positioning System (GPS)

 * u-blox GPS Modules