I started adding various items to my smoker, experimentally, many years ago. Some of the most successful have been:
Salt, table and kosher or sea salt, (great on eggs or pretty much everything)
Dill, dried
Garlic (sliced in two or three) and garlic powder,
Onions (¼"slices) and onion flakes,
Jalapenos, dried
Chili powder,
Coffee beans,
Cocoa powder, (great for molés)
Pasta, (awesome change of pace for macaroni dishes)
Rice, split peas, lentils etc.
Sardines, (oil or water packed & thoroughly drained)
Tomatoes, dried (I usually dry them in the smoker, on a screen from my regular dryer) the screen cleans up nicely in the dishwasher. Same applies to the garlic, onion and jalapenos. Et cetera!
The most successful of all has been Paprika. Smokey paprika is hard to find in the supermarket and expensive. I just dump the much cheaper Spanish variety into a foil pie plate and put it on a shelf above the meat. When the chips need replenishing I give it a good stir and continue. I`ve used every kind of wood and it`s all good. Some is kept separate, such as maple which I like to add to bacon rub but I generally blend it together for all-purpose use.
Quality control or reproducing exact results would be a desirable objective but has never been an issue with the many friends and neighbours that bring me their bulk paprika for smoking. My personal preference leans toward hickory and mesquite for all purpose use but my current blend includes those plus maple, apple, cherry and alder.
Other than the fresh items which must be dried on screens, the pie plate principal works for all powdered or granulated products.
As in all smoking, experimentation is the only way to develop a taste that fits your palate.
Check out the rub recipe that I posted on "justsmokedsalmon.com"
http://www.justsmokedsalmon.com/alderre ... PurposeRub