We keep a bag of Bob's Red Mill GF chocolate cake mix on hand for times when I'm in dire need of cupcakes. I make it with rice milk and flax meal eggs. It's really good, especially with chocolate chips mixed into the batter!
For my son's birthday, I adapted the cake recipe from Sassy Radish that I made and absolutely loved for my own birthday. I used a sorghum flour/potato starch/tapioca starch blend that I use for just about anything to replace the flour, So Delicious coconut milk yogurt for the sour cream, and Ener-G egg replacer for the eggs. Frosting was powdered sugar, Spectrum shortening, vanilla extract, and rice milk. People came back for seconds, and the birthday boy and I were the only two who couldn't have eaten "normal" cake.
Definitely check out Gluten Free Goddess. We're avoiding the same things you are plus some, and she's my hero.