mime_dump was originally written for Greg K-H (Linux Kernel USB maintainer)'s
x.sh script so he could easily process patches in MIME encapsulation in an
automated manner.
Over time I grew it into a generic and robust mime-extraction utility.
Based on a global and local config file as well as command-line options, it's highly configurable. It can take MIME-heavy messages and give you just the pieces you want, de-mime'd.
mime_dump's help option describes all of it's options as well as the config
file format.