Arduino four years ago. Of course, after about a year playing around with their bulky blue PCBs, you want to start being able to put Arduinos in projects without paying $30 a piece for the whole development platform.
ATMega328 chip online for a few dollars, and then build around it only the parts of the Arduino board you truly need. The problem is that when you buy the AVR from a chip supplier, it doesn't usually have the Arduino bootloader preloaded on it, so using the Arduino IDE there is no way to reprogram it. (Note: you can buy preprogrammed chips, but you pay a $2 premium)
I opted to buy a tube of 25 blank AVRs, which saves me money as I continually drop Arduinos into projects, but I need some way to burn the bootloader the first time before I can start reprogramming it. Of course, burning the bootloader uses a different six pin header than the serial port, so you need to either wire both headers into every project or have a separate board which you can use just for the initial burn. One board you can use for this is actually the original Arduino board, because they have the ICSP header and are often at hand, but trying to get more than a few new chips into and out again from a normal DIP socket gets tired fast. New DIP chips come with their pins bent out 20-30 degrees, so to get one into a regular DIP socket requires bending pins and a light hand as you put it in and pull it out to prevent breaking off pins.
In my next post, I'll show you one of these applications of the Arduino which profited both in size and price from not using the entire Arduino board. I'll also eventually post an update to this post showing the power supply section built (which you won't normally need, but I will need it for a future project) and the wiring to program ATTiny85s on this target board as well, but I'm looking to be rather busy for the next few weeks.