Tpstry is a new family building website that weaves your answers to questions into a tapestry of family memories, complete with photos you upload. For each question you answer, more questions pop up. Soon, memories you have long since forgotten emerge. You can also invite other family members to answer questions and write some of your own questions.
I think if this were a collaborative effort with relatives, you could cobble a very interesting family tree as we all remember the same event differently. Probably not your serious genealogy research tree but a fun one you can involve the entire family.