I'm sure we've had plenty of unusual experiences at sites! Probably, as Rupert said some way above, due to the fact we've spent so long at ancient sites that something unusual's BOUND to happen! ;)
A couple of times, on seperate occasions, we've heard the sound of a car horn being blasted as if from a few metres away, even when there's no road nearby! That's quite odd.
Also, whenever we visit Madron Well (oh, here we go again!) we start off feeling fine, but as we leave, we get the overwhelming feeling of dread. Almost as if someone's following us, which they never are, of course! The feeling follows us right up to the end of the path, when reality strikes and all is well again! It never puts us off reivsiting, but it happens, I'm sure, EVERY time!
Other than that, apart from occasional feelings of joy or sadness at various places, I can't think of anything! I keep meaning to read a book that caught my eye some months back called "Supersense" (http://brucemhood.wordpress.com/about-supersense/ - how DO you embed URLS in posts! I seem to have forgotten!), which looks at rationalising these irrational sensations. Looks interesting!
G x