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If you're late getting to the registry, you'll find that all the good gifts are taken. You could be the guy who gives the happy couple that package of dish rags, or you can purchase a very special off-registry gift that they'll surely enjoy.

Buying things that aren't on the registry can be dangerous, as the couple may not need or want them, but you could surprise them with luxurious accommodations for their first night together as a married couple. Find a nice hotel near their wedding location (you don't want to make them go out of their way for this) and book the evening of their wedding. Let them know before the big day that you're doing this for them so they can cancel any other room they may have booked, or if they've already booked something nice, you can pick up the tab for them.

To find a good hotel in the right area, we like Priceline. You can specify the star level of the hotel -- five please! -- and usually get a very good discount. You should also ask around about local Bed & Breakfasts, as they often have the nicest accommodations of all, and you won't find these on major travel search engines.