A card with a hand-written note is simple. My husband sent one to his mother in Arizona. She loves letters. Not junk mail.
Abby Durr of Silver Age Referrals shares some other ideas:
A cupcake, a flowering plant or a jar of candy to share. A book, if they like reading and you know what kind of books
A puzzle - there are certain ones for people with dementia. Preferably one that is personal. If they like birds for example, a bird puzzle.
A hand towel for kitchen or bath.
A wide brimmed sun hat
All natural hand cream- for someone who doesn’t have dementia.
A visitors journal
Water coloring kit, if they would appreciate it.
Coloring or activity book.
Bathrobe or slippers
Gift certificate to get their nails done
Anything from the Alzheimers store