Having never had the need for such a thing I can't recommend anything that I've cooked myself - but having just been on to the blog chococolatecoveredkatie she has quite a few recipes for vegan cakes - including this carrot cake.
Babycakes vegan bakery have produced a couple of books that might be worth checking out, they have quite a few vegan and gluten free cakes - both are indexed.
Good luck!