In a thick jungle setting and not strictly in Leticia itself, Omshanty is a clutch of simple cabins with kitchens and mosquito nets, with the restaurant next door serving terrific meals. Friendly English-speaking owner Kike organizes jungle excursions, and guests have been known to linger here for weeks, seduced by the jungle setting and excellent hospitality.
It's possible to camp here too (COP$10,000 per person per night), but you'll need your own tent.