Europe
South Downs Way
The South Downs Way is a 160 km bike path across South Downs National Park in the UK. One can tour from Winchester City Mill in west to Eastbourne in the east. The national trails website has good information abou the route. Here is a list of bike rentals.
Sustrans - UK Biking
Sustrans is a network of routes, many traffic free, throughout the UK. Check out their map to find bike touring routes. The green lines are traffice free.
Fimmvörðuháls Trail
The Fimmvörðuháls Trail is one of the best hikes in Iceland. The trail follows the Skoga River from Skogafoss Falls at sea level up between the Eyjafjallajökull and Mýrdalsjökull glaciers and on into the Thorsmork Valley. The trail is 25 km with 1000 m of elevation gain.
There is a hotel, a hostel, and a large camping area at the Skogafoss trailhead. By evening, the camping area was quite full. You can do the hike as an out and back from Skogafoss to the bridge. With two cars, or skill with local mass transit, you could do a through hike. There are also guided through hikes that originate in Reykjavik.
Ciro Bike Trail
The Ciro bike trail is a rail trail between Mostar and Dubrovnik on the coast.