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 Pro Trinket 3V or 5V, but when size isn't as much of a concern, and a USB-serial converter is required, we reach for an Adafruit METRO.
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.
This version of the METRO 328 comes as a fully assembled and tested development board but without any headers attached. We do include some through-hole headers that you can solder on if you like, or you can solder wires or header directly to the breakout pads. We also include 4 rubber bumpers to keep it from slipping off your desk.