There are many different gift registries to choose from such as charity, honeymoons, new homes, specialized stores.
If you choose to give to a charity it's best to avoid political or controversial causes. Examples would be Stem Cell Research, Same-Sex Marriage, or Pro Choice to name a few.
Tell your guests your intentions by word of mouth.
If asked directly then answer directly. No sense in beating around the bush. Let you guests know exactly what you would like.
It is the guest prerogative to choose what to give. So don't strong arm them into using your registry. Keep in mind your registry is not a requirement it is a suggestion for gifts.
Some people do not like to give money as a gift. So still set a traditional registry, even if contains only a few items.
