Carrot cake is a really easy cake to make. It's pretty much guaranteed to turn out deliciously moist due to the water content of the carrots. You could make this recipe as a sandwich cake with the cream cheese frosting serving as a sandwich layer in between, and on top. Alternatively you could make it in squares.
Emi's school is having a cake sale this afternoon, so I'm going down the cupcake route to max-up the number of units for the punters.