I stumbled across this cool little tool today called AquaSketch and after playing around with it, figured it was worth sharing. It uses the Tropica plant paintings among other images to allow you to make a virtual 3D image of your aquarium. It takes a bit to get the hang of it, and the plants list is not by any means exhaustive, but the most common plants are included. The final result is rough, but very handy for giving you an idea of how a basic layout will look when completed. Just for fun, I made a model of my new aquarium. Even though you can only create rectangular aquariums and mine is a bowfront, you can get a decent idea of what it will look like. It has a glosso lawn on the left, with manzanita driftwood, crypts, rotala, and some moss on the right. Not too bad, eh? You can also save your layouts so people can view them in the original 3D format. Here's mine.
