Trek	Place	miles	days	Elevation ft	Season
Annapurna Circuit1	Nepal	150	17	17,769	October
Milford Track	New Zeland	34	5	4,265	Nov - Mar
Mount Kilimanjaro	Tanzania	33	6	19,341	January through mid-March
Inca Trail Machu Picchu	Peru	27	4	14,500 2	April to October See AndeanTravelWeb.com

1. By 2012 a road will be completed up to Manang on the east; It already goes up to Muktinath on the northwest, leaving only 7.5 mi. over the Thorong La pass undisturbed.
2. Machu Picchu is actually lower in elevation than Cusco (7,874' versus 11,150').

Others:

Treks (from BootsNall):
Tongariro Northern Circuit, North Island, New Zealand 
Zion Narrows, Utah, United States 
Tiger Leaping Gorge, China 
Kalalau Trail, Kauai, Hawaii 
Torres del Paine Circuit, Patagonia mountains, Chile
Tour de Mont Blanc, France
West Coast Trail, British Columbia, Canada
Ben Nevis Blues  Ð Fort William, Scotland

Climbs (from National Geographic):
Mount Khuiten, Mongolia
Kilimanjaro, Tanzania [19,341']
The Andes, Peru [14,500']
Mount Everest, Nepal [29,035']
The Matterhorn, Switzerland [14,691']
Mount Elbrus, Russia
Cilaltépetl and Iztaccíhuatl, [Mexico 18,406']
Denali, Alaska, [20,320']
Annapurna, Nepal