You can imagine my surprise when I found a video showing how to shoot a cart out via a dispenser, then get it to turn back into an item... which is then sent back to the dispenser it came from via hoppers! What kind of black magic is required to do such a thing, you ask? Oddly enough, it uses one of the more obscure and shunned blocks in the game now - that of the lowly cactus. Take a look.
I was skeptical too, but after trying it out I'm pretty happy with the results. I haven't lost a cart to the cactus yet - what's more common actually (and still very rare) is the cart getting stuck between the glass before it hits the cactus, possibly causing a backup of carts if not removed. That can be taken care of easily with a detector rail attached to a lamp to notify you though.