The AVR Watchdog
The AVR Watchdog is an essential mechanism to protect long term run applications from code freezes affecting their functionality.
atmega328p
How to set the AVR Fusebits
Learn how to set your atmega to work with various external crystals, program the fusebits, and build a fusebit doctor to revive your AVRs, in case you wrote the wrong settings .
BMP085 Barometric pressure sensor
The BMP085 is a compact, low power sensor for reading temperature, barometric pressure and altitude. See it in use with Atmel microprocessors.