Hi,
This comes up fairly often and most people decide the amount of work it takes isn't worth the payoff.
But there are sources of information;
A really good book which features the idea of natural vivaria.
And there is also a forum which has some really good ideas;
http://www.vivariumforum.com
But think about it because it's not really an idea you can do on the cheap or half-cocked from all I've seen.
dr del