embroider towels, robes, with a monogram, or the spa's logo, depending on the sophistication of your machine....
tote bags, eye masks, turbans, small afgans

dream bags- think sachets but put your own spin on em... you can do this or any variation of it and do either a dream tea( this idea might need a little more research) with hand sewn tea bags or use one for aromatherapy. you can work with your friend to develop a signature scent... and invite people to bring a little piece of the spa with them into their everyday lives. it could be for car, work, home... and could contain a tiny bottle of essential oil with the same herbal infusion.....I think that it would be a nice gift. you might visit spa websites and check out their gift shops.... I have gotten several gifts from friends who went to spa weekends, so you could include gifts for the significant others... maybe a marry me bathroom kit for newlyweds.. monogrammed towels, and hand towels, washcloths, or one of those soft soap mitts that you put the soap inside of... well, my little brainstorm has blown over:) I hope this helps.kim chi

customize slippers or thongs with beads, flowers, embroidery, fringe, jewels...

herbal eye masks

purse emergency de-stress kits - mini sachet to whiff, oil, valerian, crystal, book, lip balm...

awesome ideas ladies, thanks so much!

i had an aunt who made "sand bags"... basically, sand salt that she put in lined draw string bags. was cute. sometimes she made up baskets (soap, shampoo, bathbubbles, sandsoap, etc) and gave them as christmas gifts.

I make those aromatherapy hot/cold bags. You can make them in any length/size, fill them with flax seed and some dried lavendar (or rosemary, or whatever you want). The cool thing is that you can either toss them in the freezer for a cold pack or place them in the micro for a heating pad.

Sumptuous little towels & wash clothes.

Perhaps little bags (fold over kits) that could contain say, manicure items or pedicure items...

Robes

Hair ties. I use my scrap velvet and make little tubes and then use regular elastic. It's always so hard finding good hair ties and big scrunchies are just so, well, big and scrunchy. On that same note, headbands.

Beauty bags & tote bags - for a fabulous day at the spa of course.