A good option for a one-night stay is Cumaceba (Putumayo 184, tel. 065/23-2229, www.cumaceba.com [1], two days/one night US$114 pp), which is 35 kilometers downstream of Iquitos [2]. The thatched lodge has nice rooms with private bathrooms, cold water, and kerosene lamps, along with a dining area, hammock hall, and plans for a swimming pool.
The lodge’s packed, one-night, two-day tour includes a walk through a patch of primary rainforest, caiman spotting, bird-watching, piraña fishing, and a visit to a Yagua village. To make up for a general lack of wildlife, guests visit a nearby family that keeps monkeys, turtles, sloths, parrots, and a pet anaconda.
Links:
[1] http://www.cumaceba.com
[2] http://www.moon.com/destinations/peru/the-amazon/iquitos