Prior to Zen based processors there are a decent number of offerings under the Opteron and AMD's embedded SoC families (possibly others, but these are the ones I'm familiar with) which did not contain ME-like capabilities. Projects like Coreboot generally have pretty good support for these AMD parts. For an embedded example, see the PCEngines APU2 boards: http://pcengines.ch/apu2.htm
Zen based parts from AMD have their PSP (platform security processor), which I believe is generally a dedicated Cortex-A series CPU within the silicon to do many security related things. Its functionality is similar to some of what the ME provides on Intel parts.
Actually AFAIK the APU2 SoC includes a PSP already, the APU1 is still free of that.
But even the APU1 SoC has a small LM32 core that you have no source for, see Rudolf Marek's CCC talk "AMD x86 SMU firmware analysis".
Zen based parts from AMD have their PSP (platform security processor), which I believe is generally a dedicated Cortex-A series CPU within the silicon to do many security related things. Its functionality is similar to some of what the ME provides on Intel parts.