Favorite trekking destinations?

Where (besides Kilimanjaro) have you been hiking or trekking? What places are your favorites? Where are you planning (or dreaming) to go next?

I want to visit South America next. High on my "hit list" are the Inca Trail to Machu Picchu in Peru (although I hear its kind of busy/touristy), and Torres del Paine park in Patagonia, Chile.