VOR-DME wrote:

I'm departing a non-towered field IFR, let's stay East Coast, and say
Bennington (KDDH), departing eastbound. There is a published departure
proceedure, for obstacle (read mountain) clearance. Under Part 91, I
am not required to follow this proceedure, but due to mountain
obscuration I may wish to do so. What do I put in my flight plan, or
in my communication via the local GCO to indicate whether I intend to
return to the Cambridge VORTAC or not? Albany approach may have other
IFR traffic coming into Bennington, so they will want to know if I am
backtracking to CAM or not.


You should file what you intend to fly, DDH..CAM.V490... for example.
Here's a note from the paragraph on Departure Clearances in FAAA 7110.65:

"If a published IFR departure procedure is not included in an ATC clearance,
compliance with such a procedure is the pilot's prerogative."

However you're actually cleared you retain the option to fly the departure
procedure.