Of course search the wedding registry. But, if you don't wish to pick something from their list, determine the theme of their list. Then expand on that with your own special gift.
Call somebody in their wedding party for some personal or special gift ideas.
Give them a wedding gift "in double" - Think of something you can give them two of that will be useful. Better yet a wedding gift they can use together.
Give them a wedding gift service you can provide personally - If your career is something they could benefit from provide your services for free.
Avoid purchasing something that might be of your personal taste. This gift is for somebody else and your gift may not go with their personal style. Neutral is best.
If sending them money, consider sending with your RSVP card. This will help the couple make upcoming plans knowing how much money they have to work with.
Consider creating a photo album of friends at the wedding and at the reception. Professional photographers normally only concentrate on the bride and groom.
Make a romantic occasion even more special for your loved one with a love message. Whether it's for an anniversary, wedding, engagement, valentine's day or just because, say it with a love message.