I'm a big fan of millet + banana +coconut or nuts. I prefer to warm it in the microwave to take the refrigerator chill off. Or, if you have an indian or asian grocery nearby, you can get plain puffed rice and millet, which might be good in a traditional granola recipe.

I make a great crunchy granola with lentils...first cook them, cool and use instead of oats in any granola recipe. grain free granola with protein! buckwheat is great as well, I don't see a problem using in the same way as oats...
Now that i think of it, you can use rice too and bake it into granola, why not.

I've been "trying paleo" for about two weeks...so far so good. But my standard cereal in the mornings before was Kashi's Go Lean Crunch! I got this recipe, made it (couldn't find dates in my farmer's market sou doubled up on the cranberries. Loving it so far....though I did burn it a little.
http://paleoparents.com/2011/grain-free-granola/

I'm not sure exactly how they'd work on their own, but I've used quinoa flakes in muesli in conjunction with rye or oatmeal. It might take some experimentation, but I bet would be good in a mix with seeds and nuts. (However, some quick google searching suggests that quinoa flakes may be processed in facilities that also process wheat, oats, etc., so it would be important to be sure you had a gluten free source.)

I like to put kamut or buckwheat in my granola. They're not the flakes you'd get from oats, but they'd beef it up. Also, it's possible to roll any grain. Although oats are the most common, you can find rolled or flaked kamut and buckwheat, which you could substitute into most granola recipes. I know I've done it with rolled spelt before (I know, not GF). Or, if you wanted to, you could even buy your own roller.

This isn't for granola per se, but I recently made some no-bake hemp seed peanut butter (or sun or soy butter) granola balls with quinoa flakes instead of oats. They are super quick to whip up and are to die for:
http://foodforthoughtlinds.blogspot.ca/2012/07/healthy-no-bake-hemp-seed-peanut-butter.html I suspect you can use quinoa flakes in place of oats in a lot of granola recipes.

I'm also about to post some super delicious granola bars with flax, chia, hemp, etc. in the next few days. Again, they have oats, but I'm pretty sure the quinoa flakes would work here too.

I've used puffed millet and puffed corn granola along with oats, but I think it would be fine without. I've used Alton Brown's and Ina Garten's recipes.

I once ran across this recipe but never made it because I don't own a dehydrator: http://www.fortheloveoffoodblog.com/2012/05/raw-sprouted-buckwheat-granola.html
However, you could probably bake it at a low temperature in the oven.

This might not be exactly what you meant but I'm allergic too and I LOVE Mesa Sunrise's amaranth, quinona and flax cereal. I use it in my yogurt too. The brand might be Nature's Path, if I remember right. Whole Foods sells it.

Oops, it might have corn in it too. But it says it's gluten and wheat free. By the way I was diagnosed (with a blood test) allergic to wheat and not gluten. I discovered that the label "gluten free" is regulated by law, "wheat free" is not. So be careful out there.

Flax, almonds, chia seeds!