So I took the map in the Dragon Age RPG Set 1, a ruler, and sat down to map out distances to our favorite places in Ferelden. These measurements were taken along road routes where available on the map to be as accurate as possible. Of course, in the end it's all approximate.
Denerim to Amaranthine = 72 miles
Denerim to Highever = 162 miles
Amaranthine to Highever = 108 miles
Denerim to West Hill = 198 miles
Denerim to Lake Calenhad Docks = 252 miles
Denerim to Circle Tower = 270 miles
Denerim to the mouth of Gherlen's Pass = 324 miles
Denerim to Gates of Orzammar = 351 miles
Mouth of Gherlen's pass to Gates of Orzammar = 27 miles
Denerim to Dragon Peak = 18 miles
Denerim to Lothering = 180 miles
Denerim to Redcliffe Village = 270 miles
Denerim to Redcliffe Castle = 288 miles
Denerim to Ostagar = 243 Miles
Denerim to Gwaren = 252 miles
Denerim to South Reach = 117 miles
Denerim to Haven = 342 miles
Lothering to Redcliffe Village = 90 miles
EDIT: got a request for Circle Tower to Lothering, figured I'd add it in: 198 miles