Tom, Teo I set ourselves the goal of paddling 3000km down the Yukon River last summer. This unguided and unsupported adventure across North America took us 6 weeks and through some of the world's most beautiful and scarcely populated wilderness areas.
Our total lack of kayak/canoe experience made it that much more exciting (/daft). Highly recommended!
http://www.exploringtheyukon.com/