The ADXL337 breakout is a small and compact board that can measure the acceleration.
Thermocouple amplifier is an outstanding analog-output amplifier that is easy to use.
SparkFun Humidity and Temperature Sensor Breakout - Si7021 is an easy tool,less expensive board that can detect both humidity and temperature.
Thermocouple Type-K - Stainless Steel is a device used for measuring temperature using wires of different metals.
SparkFun BME280 Atmospheric Sensor Breakout measures the differences in pressure found in the atmosphere.
Humidity and Temperature Sensor - RHT03 is a cost effective way to measure the temperature and humidity.
FLiR Dev Kit is an IR imager breakout with thermal imaging option.
This pressure sensor from Freescale is a great low-cost sensing solution for precision measurement of barometric pressure and altitude.
The BMP180 from Bosch Sensortec is the latest in the line of barometric pressure sensors and this breakout board makes it easy to interface with an Arduino.