The Unst Bus Shelter website has been updated, and remains as charming as ever, 10 years on. It has been occasionally mentioned on the Blue, but the new version of the site shows that it just keeps on getting better. The shelter has even been praised by UK film critic, Mark Kermode who visited it when it doubled as a two person cinema. It has also hosted the crown jewels, beer drinking hamsters and music festivals.
Follies and Monuments Devoted to the history of English architecture fantastic, outrageous, and (to borrow from the quotation on the index page) "useless." See also this 3D model of William Beckford's Fonthill Abbey (and the facsimile reprint of A Description of Fonthill Abbey and Demesne); folly gardens, historical and current; and a famous French folly garden, the Désert de Retz.
World's Largest Collection of World's Smallest Versions of World's Largest Things. If you need that explained, you're in luck. Consider it the ying to this thread's yang.
A Sightseer's Guide to Engineering. Engineering sights around the USA.