I used to use small rubbermaid containers, like the kind a single sandwich will fit into. It worked great for my corns, but sometimes I couldn't close the lid with eggs from larger species. This year I found a new type of rubbermaid -- they have the same dimensions (I'm guessing around 7x7") but are deeper (maybe 3"?) and have clear lids. I really like the idea of being able to see into the container without having to remove the lid. As far as medium goes, I've only ever used vermiculite for incubating, and it works great.