gosh it really depends on what you mean by sacred site. I guess maybe some time in this lifetime I would love to do a Buddhist pilgrimage, although I am no longer a practicing Buddhist and have not been for 15+ years. http://en.wikipedia.org/wiki/Buddhist_pilgrimage
I've visited a long list of Abrahamic sacred sites in the Levant, none of which were sacred to me. It was fun and interesting though. I'd like to see Vatican City, Medina and Mecca too - and maybe some Tibetan monasteries.