I bought some of those little yellow gel balls to clean my kitchen disposal. The citrus smell only stayed with the disposal less than a day and I didn't feel like it did the job of cleaning the blades.

So, I sliced a lemon and froze the slices on a cookie sheet in the freezer. After they were frozen, I bagged them and kept them in the freezer.

Drop a frozen slice in your disposal and voila, a clean smelling disposal!!!