I make gluten free bread in a bread maker, however I can never get it to rise as much as 'regular' bread and is usually a little heavy. What techniques/recipes/substitutions can I try to get my gluten free bread to rise more?  I currently use a recipe that is similar to this one here, but with a bit of tapioca starch instead of buckwheat flour. 
You need something to make the batter a little more sticky so that bubbles from yeast or baking soda stay trapped as the bread bakes.  I generally use a little bit of xantham gum and a couple of tablespoons of arrowroot flour.  To make sure they're fully hydrated (for optimal sliminess) let the wet batter sit for a couple of minutes before adding baking soda.  A little lemon juice or vinegar in the wet ingredients will help too. 