I love bath bombs, particularly the ones by Lush. I especially like when they release things in the water, like soap flower petals or glitter. Bath bombs can be expensive, though. A Lush bath bomb goes for about $5 each. Of course, they are on the high end, but still, any price is high when you consider that bath bombs are merely a combination of baking soda, citric acid, corn starch, oils, and salts.
At least, that’s according to this how-to on making your own bath bombs on Instructables. Looks like it’s a matter of mixing all the ingredients together and them putting it in molds–in this case, they used Christmas tree ornaments that open to hold things inside. The end result looks as good as most of the store bath bombs you can find. They would make an impressive gift for very little cost.