My son is turning one in April and since his party will contain mostly adults, I decided to furnish each person with a small memento of the occasion.  I made card style picture frames (just large enough to hold a Polaroid photo) out of heavy paper and decorated the outside with "theme" stickers...his were "Bear in the Big Blue House". I wrote a short message on the inside thanking them for attending and at the party I took a picture of each guest or group of guests with the Birthday Boy.  I taped each photo to the frame and gave them out as the guests were leaving.  They have a permanent reminder of my son's first birthday party!