United Kingdom
When it comes to workouts and hiking, I appreciate that there are far more glamorous locations than this, but there's a recession on!
The section of the Hadrian's Wall national trail between Chollerford and Walton is a proper two day workout - especially so if you carry a full pack with you. Unrelenting ascents and descents over about 30 miles - if you mean business, this is a perfect two day walk with time to explore the odd Roman fort. If you're in poor fitness I wouldn't try to do it in two!
The beauty of it is that you can exercise in stunning surroundings with rolling hills as far as the eye can see. And if all the exercise gets too much for you, there are some excellent country pubs along the way to tempt you to break your new years resolutions!
www.nationaltrail.co.uk/hadrianswall/index.asp?PageId=1 the national trail website has links to maps and transport information - there are lots of stations on the local Newcastle to Carlisle route that will drop you off near the trail.
www.hadrians-wall.org/ has a helpful set of brochures of each section of the trail that lists all the accommodation available - from quirky bunkhouses to top notch B&Bs.