We sure love the ATmega328 here at Adafruit, and we use them a lot for our own projects. The processor has plenty of GPIO, Analog inputs, hardware UART SPI and I2C, timers and PWM galore - just enough for most simple projects. When we need to go small, we use a Metro Mini or a Trinket M0, but when size isn't as much of a concern, we reach for an Adafruit METRO. This is the Adafruit METRO with headers. It comes with headers soldered on. It's a fully assembled and tested board with through-hole headers attached. If you don't want a Metro with the headers attached for super-slimness, check out our Metro without Headers. METRO is the culmination of years of playing with AVRs: we wanted to make a development board that is easy to use and is hacker friendly. At the heart is an ATmega328P, with 32KB of flash and 2KB of RAM, running at 16 MHz. It comes with the Optiboot bootloader already installed, and is Arduino IDE compatible.