Pain relievers like Tylenol or Advil. Band aids (DH always has band aids in his billfold and saved the day for me and our kids many times-its a family joke). Small notebook and pencil. These items can be carried in your purse.

I like to bring an old flat sheet to lay out a project on the floor. Sometimes the design walls are all in use. (Sometimes the design walls get 'claimed' by a half dozen people, who leave their completed tops on them the whole weekend.....but our group tries to spread the word to minimize this.)

Don't forget the power cord and foot petal for your machine. I almost forgot to take clothes and toiletries to my first retreat. I had my jeep all packed with sewing things, stood at the door thinking, "I'm missing something." Glad to have listened to my inner warning system.

I get little address labels all the time in the mail. I put one on every item I take when I take a class. If they fall off no big deal but it is a way to avoid getting items mixed up.

Remember your prescription medications.

The more remote the retreat is, the more important it is to remember one's personal "necessary" items.

You got great tips. There is one thing I do before leaving from home. I clear a table and put my machine up and start working on what I will bring. I often find what I forgot, a new needle, small cutting board, piecing foot, traveling iron, power foot for your machine, etc. Then meticulously pack everything. I agree on labeling everything with your name. It is no fun getting to where you going and finding out you are missing something crucial like your piecing foot.

Agreed. It is much better if you can bring your own chair. Most times they have "conference/hotel" chairs.

I bring extra rotary cutter blades, sewing machine needles, bobbins, thread, seam ripper (argh), painter's tape, a small trash bag to tape to your table for trash. I also take a book with general, beginning quilting info that has measurements for quilt sizes, setting triangles, etc. Hope you have a great time.

Some sort of name tag is always welcome, and whatever you need for the intended project being done. Otherwise, my only advice is to be sure to mark EVERYTHING with your name

Our group has frequent Stitch Camps, what gets forgotten the most is a good heavy duty extension cord with multiple outlets, and amazingly the sewing machine power cord if they bring the machine they use at home. Another handy item is a plastic grocery store bag that you can tape to your table for the bits of thread, fabric that gets snipped off.
Have fun, I love Stitch Camp.
If you think you'll be going often the folding wagons sold at Sam's, etc are fantastic, I fill it up at the car, wheel it to my table & go back for 2nd load, so difficult to pack light.