Unst on Wikipedia.

Baliasta, the ruins of Baliasta Kirk, formerly Hillside Free Church. Last used in 1959. Two additional view - 1, 2. All © Tim Flitcroft (2013).

Baltasound, St. John (CoS, 1825-7). HP 615 088. © Tim Flitcroft (2012). Link.

Haroldswick, Methodist church (1990). As the sign in the photo says, this is the most northerly church in the British Isles. Its predecessor stood immediately adjacent to the north-west, where the car park is now. HP 6460 1335. © Martin Briscoe. Another view, and two interior views - 1, 2, all © Tim Flitcroft (2012). Link, which includes more photos. An aerial view is available here, showing church and car park. Both of these churches are successor to an older church (Wesleyan) which stood at HP 6442 1350, and hence more northerly yet than the current church. A map of 1880 shows it, but it had been replaced by the time of the 1901 map. A 2010 Streetview shows what remains of this church, here.
Former Church (CoS). HP 6369 1266. © Tim Flitcroft (2012). A 2015 Streetview shows that the "cafe" sign has gone.
Canmore notes the remains of another church at HP 63573 12688. The Streetview van passed it in 2015, here. The remains can be seen as grassy mounds within an enclosure wall in the middle distance. It can be seen better in this satellite view.

Lund, the ruins of St. Olaf. An additional view, and the "interior". All © Tim Flitcroft (2013).

Uyeasound, Church of Scotland (1843). HP 601 011. © Tim Flitcroft (2012). Link. Grade B listed - link.