If you are interested in doing some real amazon hiking and stick close to Manaus, you can go to some of the Islands in the Amazon side of the city (if it isnt flooded - when the river is hige these islands COMPLETELY disappear). The hike can be an hour on five and is a great day or half day trip. If you want to do a whole tour you can sing up with one of the companies at the Hotel Tropical and for 50R$ go to the meating of the waters (cool), guided hiking on an Amazon Island, and visit the opera house. The hiking is cool and guided so you will learn a lot about the amazon flura and fauna.
I cannot say enough about the gigantes lilypads which are found only in the still waters that the local tour guides know how to get you to in their canoes.
They are, to say the least, stupendous.