Via an open-source, third-party tool called me_cleaner it's possible to partially deblob Intel's ME firmware images by removing any unnecessary partitions from the firmware, reducing its ability to interface with the system. The me_cleaner works not only with free software firmware images like Coreboot/Libreboot but can also work with factory-blobbed images. I was able to confirm with a Coreboot developer that this program can disable the ME on older boards or devices with BootGuard and disable Secure Boot. This is all done with a Python script.
Those unfamiliar with the implications on Intel's ME for those wanting a fully-open system can read about it on Libreboot.org.
ME_Cleaner has been tested with boards ranging from Nehalem to Skylake with ME engines ranging from 6.0 to 11.x. With the exception of some Ibex Peak boards and not yet testing Broadwell mobile systems, ME_Cleaner is working as outlined via this matrix.
Those wishing to learn about ME_Cleaner for trying to eliminate Intel's Management Engine form your system as much as possible can visit the GitHub project site to learn more.