avrdude is a program that you use to download compiled software to the (excellent)
Atmel AVR line of microprocessors.
Trying to install the current avrdude via MacPorts can hit a snag though, because there is a flex source file (lexer.l) which won't compile with the version of flex that MacPorts installs (if you have ever installed flex via MacPorts).
The Apple supplied flex is fine, so the Portfile just needs a little addition to point the ./configure in the right direction.
Edit the portfile:
/opt/local/var/macports/sources/rsync.macports.org/ release/ports/cross/avrdude/Portfile
And add the following line to the end:
configure.env-append LEX=/usr/bin/flex
Now you just need to rebuild:
sudo port clean avrdude
sudo port install avrdude
Job done!