Haven't see this mentioned anywhere, so...
http://www.heritageopendays.org.uk/directory/town/Dover for full details
Dover College
Grand Shaft Staircase
Maison Dieu House
Maison Dieu/Dover Town Hall
South Foreland Lighthouse
St Edmund's Chapel
St Mary the Virgin's Parish Church & Bell Tower
St Radigund's Abbey Guided Tours
The White Cliffs of Dover !!!
Unitarian Church