Chris Noessel has written a splendid thing over on Medium about finding and looking after speakers, if you're a conference organiser.
I have one little extra thought to add.
1. Chris says this about getting gifts for speakers:
"Small tokens of appreciation are not needed, but always endearing. They don’t need to be expensive, but something local like art, food, or non-gimmicky technology is best. It should be something they can use, but also something they might pass on to their family/sweetheart as a gift for having to be away. With that in mind, avoid just putting a logo on schwag, as that just feels like advertising, rather than a token of thanks."
All true. One other thing I'd encourage you to think about - your speaker may be about to get on a plane, they might be trying to avoid checking anything in. Don't get them, for instance, a massive bottle of champagne or a huge metal fruit bowl.