AVRDUDE (or avrdude) is a popular, open-source, third-party (i.e. non-Atmel) command-line utility for programming Atmel microcontrollers.
It supports a wide-range of programmers and microcontrollers.
The Micro Won’t Program, What Do I Do?
Sometimes the bit rate that the programmer is trying to talk to the micro at can be a little to fast. You can slow it down with the bit rate option (-B). The bit-rate option requires a floating-point number which determines half the period of the programming waveform, in microseconds. That’s right. Half. What? So -B 2.5 would set the period to be 5us, or 200kHz.
Do NOT get this confused with the baudrate option (-b), which determines the serial baudrate at which the computer talks to serial-based programmers at.