This part of Skye is in the Strathaird estate which used to be owned by Ian Anderson (so the Jethro Tull song is a definate reference). I visited the site in summer 2003. It's in a hugely atmospheric location overlooking Loch Slappin.
Visited this site in Summer of 1997. Easy, short hike from SouthEast of the village of Kilmarie (cross stepping stones at the mouth of the burn, Abhain Cille Mhaire, and basically hug the coast on a fairly well-marked trail heading basically East). Site was fully accessible, in good shape and interesting - well worth the trip. The entrance was partly collapsed, but open.
Side note: the rock band Jethro Tull (on an album called 'Stormwatch') has a song called "Dun Ringill". I do not know if the song references this site (I've not seen another of this name) or some imaginary place. Any Ian Anderson/Tull fans out there know?
On the subject of the Jethro Tull references, last night at Reading Hexagon, they played Dun Ringill. Ian Anderson introduced it as a song about a neolithic (sic?) hillfort & went on to talk about it being used to try to see off the Vikings....
He's usually reasonably knowledgable about stuff, so I suspect he was simplifying it for the plebs in the crowd. Or not.