Although it isn't the easiest of projects, it's one of the most interesting we've seen for a while. Created by Arduino team member David Mellis, his "DIY Cellphone" emulates the features of a basic GSM handset from the turn of the century. Based around the ATmega1284P running the Arduino bootloader, it has the ability to make and receive calls, text messages and work with a basic phone book. If you're interested in making one for yourself, David has published all the design files for the PCB, laser-cut enclosure and the BOM to help find the required parts without too much effort.
It's a great extension of the Arduino ecosystem, and perhaps something that once made will certainly show your ability for construction - so visit the project site for all the details. And for more, we're on twitter and Google+, so follow us for news and product updates as well.
Are you interested in Arduino-compatible boards running more powerful microcontrollers such as the ATmega1284P? Then stay tuned as very soon we'll have the Goldilocks board - an excellent upgrade to your Uno-compatible projects, with so much more:
With a faster 20 MHz speed, eight times the SRAM, four times the flash memory and EEPROM of Elevens and Uno-compatible boards, plus a myriad of other features - the Goldilocks will be one of the most powerful and versatile boards in this space. For more details, check out the product page.