I've been invited to a dedication ceremony and reception (someone is being honored by having a building dedicated in their name. What type of gift is appropriate for such an occasion? Are gifts in order?

Gifts are not typically in order. Assuming that the organization is a non-profit (school, hospital, church, etc), you might consider making a donation to the organization and note that it's in honor of the person. If you were running the ceremony you might consider some sort of memento to be presented to the donor (such as a framed proclamation from the board of directors), but attendees to this type of ceremony don't normally bring gifts.