After the engagement, bridal shower, and wedding, coming up with a unique honeymoon gift idea can be a challenge! Most people don't give the couple a gift for their honeymoon--but, if it's something that you'd like to do, here are some ideas:
Give them a basket full of items according to the theme of their honeymoon. For example, if it's a beach honeymoon--beach towels, sunscreen, aloe vera, flip flops, disposable waterproof camera. For a skiing honeymoon--hats, mittens, scarves, handwarmers, chap stick, warm socks, disposable waterproof camera. Give them the basket ahead of time so that they'll know what they won't need to purchase.
Find out what hotel the couple is staying at, and have a bottle of champagne/wine and/or flowers waiting for them upon their arrival.
Call the hotel they're staying at ahead of time to find out what good restaurants are in the area. Purchase gift certificates to those places.
Buy them a book about the area they're going to.
Pay for a couple's massage at the hotel/resort they're staying at. If the place they are staying doesn't offer this, find a massage parlor nearby and pay for the massages in advance. The couple will love this after all of the stress of planning the wedding!
Give them an empty scrapbook or photo album to fill with photos and memorabilia from their honeymoon.
Have two plush robes mongrammed--"Mr. Lastname" on one, and and "Mrs. Lastname" on the other