Besides the obvious hooks (wood is a nice gifty thought) and yarn, how about a subscription to a crochet magazine. Crochet Today, Crochet!, Interweave Crochet etc.
Or one of the little medallion yarn cutters? I have one now..would have loved one a long time ago. They look cool and are very handy..not something you would buy for yourself. Or a really cute pair of little scissors or a fun tote for carrying your small project (I like zippered cloth bags)