I love baking from scratch, almost all of my cakes are from scratch...However, the convenience of a box mix is hard to turn down. So, I've started making my own "from scratch" cake mixes that I have on hand at all times. Basically, it's all the dry cake ingredients, sifted together, put into a gallon sized freezer bag, with a label that states what cake the mix will make and lists the measurements of the wet ingredients that need to be added.
I bake A LOT, I have a few cakes and several dozen cupcake orders each week. So every Sunday night when I have some free time, I make up these cake mixes so when it comes time to bake all I have to do is dump the mix in a bowl, add the wet ingredients and bake.