I have made a farm that's styled as a large tree.
The inside of the tree has a ton of cocoa pods growing. I don't really know why I did this.
There are four lanes that have a different crop in them. There is currently carrot, wheat, and potatoes growing in three lanes. The fourth lane will be for Beetroot when 1.9 is released.
Each lane should be able to contain 248 crops. When crops are ready to be harvested, a single press of a button will bring down water into hoppers, which is then fed into a large chest.
The essential parts of the farm are finished. All that remains is to make the thing look like an actual tree, which is going to take a lot of jungle leaves.
It took me a lot of jungle logs and leaves to make it. I think it's worth it. It's probably the nicest looking thing I've made in Minecraft.