Before 14w29a I used this automated furnace:
[ ][C]
[C][H]
[H][F]
[ ][H]
[ ][C]

Where:
[C] - chest
[H] - hopper
[F] - furnace

I used it for large amounts of cobblestone or clay. As fuel I used Lava Buckets loaded to the left chest. When lava from bucket was used by furnace empty bucket drops to the chest via hopper.

But after 14w29a this mechanics was broken and now empty bucket stays in the fuel slot of the furnace. See the pictures.