Hand out invitations to a Christmas or Christmas Eve service to your neighbors.
Is there anyone at church today who has encouraged you by their example of connecting with their neighbors? Let them know. Thank and encourage them.
If today is your last shopping day before Christmas, can you get anything for a neighbor? Don't worry about it being "Christian." Let it communicate love.
Don't forget to thank the host of a Christmas party. Maybe send them a picture of you and your white elephant gift.