evilmadscientist.com writes: [via]
Reading out the flash memory is straightforward with an AVR ISP programmer, such as the USBtinyISP, using avrdude from the command line. You’ll need to have a copy of the AVR toolchain– or at least avrdude –installed on your computer. There are easy installers available for Mac (Crosspack) and Windows (MHV AVR Tools) that include this software, along with the other open source tools for AVR development. Linux packages for AVR development are also available.
AVR Basics: Reading (and writing) flash contents – [Link]