Horses & donkeys galore! I started a random world and spawned in a huge plains biome with horses right in front of me. Just running around for 5 minutes I found 25 more horses and 10 donkeys.
There's a small ravine nearby just off a river with tons of iron and coal - easy access if you break 1 sand block and ride the water down.
I did some mining inside the ravine, quickly found an abandoned mineshaft with tons of chests - sorry, didn't get the coordinates yet but if you do some strip mining under the ravine you're bound to run into it - it's huge!