Make sure you read BTU Values of other grains.
Other grains can be burned in corn stoves without problems. Sometimes some stoves will have feed problems in the auger system that might cause the grain not to be fed into the fire. A good suggestion would be to buy a very small quantity of the grain first to do some trial burns. Make sure the grain burns well and that it feeds through the grain deliver system and into the firepot without jamming or snuffing out your fire.
Many times other grains have different types of garbage in the grain that could cause your stove problems. Oats have straw that could plug the feed auger, but as long as the straw is all removed, they burn great! Oats have close to the same BTU per pound value as corn, but they are lighter (32lbs/bu); meaning you have to burn more. You may find that they will be fine for use in the spring and fall but once the temperatures really drop, your stove could not make enough heat, even with the feed rate to the max.
Another grain that is popular is to burn rye. It burns as hot or hotter than corn. It makes clinkers that look like lava rock. Rye is generally quite cheap to seed and plant, and you can go directly from the field to the stove if you harvest at the right time (no drying like corn).
Barley can also be burned. It weighs 48lbs/bu. ID Farmer reported success burning barley in his Bixby stove when blended with pellets to prevent bridging of the light kernels in the burnpot. This likely wouldn't be an issue with stirrer-type burnpots.
Buckwheat has been tested successfully in a Bixby stove. See the following thread for photograph, discussion, and some data. http://forum.iburncorn.com/viewtopic.php?t=2976&highlight=buckwheat Like rye, it is relatively inexpensive to grow and to harvest. It is commonly grown to improve soils and to smother weeds.
Canuck reports burning a mixture of lentils, barley and rye in his Harmon PC45 with a bit of pellets mixed in to help the burn http://forum.iburncorn.com/viewtopic.php?t=12103 .
Beet pulp pellets are another option as discussed in the following thread. http://forum.iburncorn.com/viewtopic.php?t=1117&highlight=beet+pellet
Many stoves can burn cherry pits including the Bixby stove http://forum.iburncorn.com/viewtopic.php?t=8128 . One thing to be aware of, cherry pits contain cyanide (hydrocyanic acid or called prussic acid). At 300 ppm it will kill a human being in a matter of minutes. The pit also are highly toxic (only if cracked or halved) to small children and pets if ingested. Ingested cherry pits are not digested and will pass through the gut. As long as the cherry pit is not cracked open the poison kernel part of the pit can not be absorbed by digestion. Cherry pits are very hard and opening one with the teeth isn't likely. However, this all said, cherry pits do make a very good fuel and can be obtained very economically as many cherry canning factories give them away as waste product. I imagine they smell real nice in your house too. Reports are that they burn cooler than corn with more ash. Maybe good for warmer climates or spring and fall here in Wisconsin. According to Nogaspains "They burn quick and very hot. They feed in the Harman close to the rate of corn, but because they were a little bigger, had to turn the feed rate up just a little. The smell is wonderful when they burn... They burn great with a mixture of corn and pellets too." Blume98 is less impressed: "Very dirty, high ash, hollow so the feed rate has to be bumped up a lot. Burned 1 year. Got free. Never again."
There are also Grass Pellets and various types of biomass pellet. Nealbea, for example, reports success with homemade oak leaf pellets in a Bixby stove http://forum.iburncorn.com/viewtopic.php?t=11800 .
Farmer1 reports success burning black sunflower seeds in a 1020 American Royal Biomass boiler. He says "...no clinkers but more fine ash just have to clean the ash out from around the air holes more often than with corn. Cuts the air flow so it doesn't burn quite as clean but i do like the heat the sunflowers are giving off. I don't get the sudden temp drop when a large heat load is applied like i do with corn the recovery is def. faster."
Farmer1 also reports burning a mixture of fines, whole corn, sunflower seed and oats. The whole grains help to loosen the fines.
Weed seeds, specifically a ton of ragweed, have been burned successfully by Farmer1.
IDFarmer reports burning wheat successfully in a Bixby stove. He says "I do know it seems to burn hotter and cleaner then pellets. The only downside I have had so far is that at start up it will blow some of the wheat up out of the (burn)pot." Olf20 reported similar blow-out problems while burning wheat in a Countryside stove equipped with a modified clinker-type burnpot. Olf20 added that the burn was harder to control in the Countryside than for corn but clearly not so difficult as to deter burning wheat over a period of 4 years.