Well, I've used aspen, eco earth, cypress mulch, reptibark, and reptichip. Aspen is great for snakes like hoggies and kings, but for snakes that need more humidity it sucks because it molds when it stays damp too long. Eco earth works, but gets in the water dish and sticks to anything wet. Cypress mulch works too, but doesn't absorb terribly well and I worry about it possibly being a danger if ingested. Reptibark has poor absorption and once dry really doesn't help help the humidity much. Reptichip so far is working well for me, it seems absorbent, holds moisture, and looks nice to boot.