Mel, I love this idea for a thread! Accentuate the positive.
I adore those kinds of message-in-a-bottle experiences such as you describe in your opening post. Something I do, somewhat along those lines, is when I drop pennies, I leave them, letting someone else find a "lucky penny" later, if they choose to see it that way.
Learning something new that's fun and interesting never fails to brighten my day. I'm a fan of royalty (and yet an ardent republican [lower-case 'r', mind you]--go figure), and one of my favorite royal personages is the late Queen Emma of the Netherlands (1858-1934), who was born a Princess of Waldeck and Pyrmont, and ruled as regent for some eight years for her daughter Queen Wilhelmina. One day I came across, leafing through a book on the crown jewels of Europe, a photograph of Queen Emma as a young woman, resplendent in her royal regalia. Previously I had only seen images of this lady as a mature woman, dressed in widow's weeds. A whole new facet of this princess's presence was revealed to me, and I was on Cloud 9 for the rest of the day.