On the subject of cakes, here is another really easy one. I just made this for some friends and it got rave reviews.
1 box white cake mix
1 can sweetened condensed milk
1 can cream of coconut
1 small tub Cool Whip or whipped cream
Mix and bake cake mix. In a separate bowl, mix milk and cream of coconut. While cake is still warm, poke holes all over it (you can use the other side of a pen), then pour the milk mixture over cake and let cool. Top with Cool Whip and sprinkle with coconut.
The milk soaks into the cake so that it tastes like Tres Leches, I think. One warning is that this is pretty sweet, so I think next time I might try using angel food cake instead of the white cake, but I'm not sure how that will turn out. The original recipe is definitely still delicious though, so enjoy!