As far as the pyramids go, as one aspect of this discussion, I will offer this:
Over the course of decades and centuries, a lot of knowledge becomes forgotten, lost, altered, etc. Progress brings about new ways of doing things and the old ways fall into disuse. There are plenty of things that were 'all the rage' back in the 1800's, but which are not seen anymore today.
The builders of the pyramids may not have had any extraterrestrial help. They may have had knowledge developed on their own that was subsequently lost.
This man may have rediscovered it:
http://en.wikipedia.org/wiki/Coral_Castle