I have my own soap making business, so I have tons of recipes for making your own balth salts, facial masks, bath oils - lots of neat stuff for gifts. If there is something in particular you are wanting to make. let me know. I probably have a recipe. Here are some more bath ideas:

Ocean Bath

4 cup coarse sea salt (look at natural food stores)
few drops of fragrance oil (optional)

This looks pretty for a gift if packaged in a glass jar. Add a large shell for a scoop and add these instructions: Use 1/4-1/2 c per bath.

Fizzing Bath Crystals

1/2 cup baking soda
1/4 cup citric acid (look by canning supplies)
2 Tbsp cornstarch

Mix well and store in a dry, airtight container. Fill tub with warm water and when full, sprinkle 1/4 cup in bath. For a little more fizz, increase citric acid to 1/3 c.

Milk Bath

1/2 c powdered buttermilk
1/2 c powdered milk
2 Tbsp cornstarch
2-4 drops fragrance (optional)

Mix well. Use 1/4 cup per bath. (you may want to actually sift these ingredients to get them blended well)

ENJOY!