Mike Pitts floats an interesting theory that the post holes, ditches and stones at the north east entrance to Stonehenge may have been a Mortuary Enclosure - details at his blog - that pre-dates the stone phases of Stonehenge.
But those post holes are only some of the many we know about, and there is much of Stonehenge we don't know what post holes are or were there.
(Click for larger)
Joining the dots and making some sense of them is not easy, though an "avenue" or ceremonial entrance way can be imagined from the south entrance. And alignments can easily be constructed...
The story of Stonehenge before the stones is a fascinating one that is waiting to be written.