It's not an idea for a party but thought I would pass it along. 4 yrs. ago, my in-laws had their 50th. 6 months prior, I sent out letters to 150 names, which my sister-in-law and I found after sneaking my MIL's address book out of the house for a few hrs. I asked them for a note to the anniversary couple, and also to include pictures of themself and maybe any pics they had of themselves with mom and dad. I got letters back from couples they had been friends with when they first got married, my FIL's buddies in the service and lots of other's they had exchanged Christmas cards with but hadn't seen in a very long time. I made a scrapbook out of all the things I received and gave it to them on their anniversary. They were so touched by it and spent hrs. pouring over all the letters and reminiscing about the things they read. It was on the guest table at their anniversary party and they now keep it on the coffee table and still look at it occassionally. It meant more to them than anything we could have bought them for a gift.