1. Decorate a tree in public. In a park, on a street, outside your workplace, places you would least expect it.
2. Leave tiny anonymous gifts with notes that say "something for you".
3. Put fortunes written on paper into people's pockets when you go to parties.
4. Write letters telling people you admire them and that you're greatful for their existence.
5. Buy a tree for someone else.
6. Write peaceful quotes in public places with chalk.
7. Guerilla carolling...Sing x-mas carols on people answering machines.
8. Plant some bulbs in pots, place them in locations that could use some life.
9. If you live in a snowy climate write large notes in the snow on people's front lawns (when they are out). If you live in a warm climate you can hang greetings in the trees.
10. Make a treasure map of the best x-mas lights in your town. Hand it out so people can do a tour.