Adafruit PID 2000 Pro Trinket - 5V 16MHz ATmega328P onboad chip in QFN package 16MHz clock rate, 28K FLASH available USB bootloader with a nice LED indicator looks just like a USBtinyISP so you can program it with AVRdude and/or the Arduino IDE (with a few simple config modifications). Also has headers for an FTDI port for reprogramming Micro-USB jack for power and/or USB uploading, you can put it in a box or tape it up and use any USB cable for when you want to reprogram. On-board 5.0V power regulator with 150mA output capability and ultra-low dropout. Up to 16V input, reverse-polarity protection, thermal and current-limit protection. Power with either USB or external output (such as a battery) - it'll automatically switch over On-board green power LED and red pin #13 LED Reset button for entering the bootloader or restarting the program.