My recollection as a child growing up in Janesville was making little baskets out of construction paper; finding violets and dandelions to put in them; and creeping up to the front door of neighbor's homes to place the basket on the doorknob or doormat, ring the bell and run.
If Wikipedia can be believed, baskets were part of the May Day event: May Day was also celebrated by some early European settlers of the American continent. In some parts of the United States, May Baskets are made. These are small baskets usually filled with flowers or treats and left at someone's doorstep. The giver rings the bell and runs away. The person receiving the basket tries to catch the fleeing giver. If they catch the person, a kiss is exchanged.
I was too young to understand or even know about the tradition in the last two lines here; if I had, my entire May Day strategy would have been much different and different doors would have had bells rung!
The same listing also mentions the celebrating of May Day seemed to fade as it coincided with the annual show of force of the Soviet Union on May 1 with it's large parade of military forces and weaponry.
This seems like the kind of tradition that could be revived and is much more personal than an e-card you might fill out during your morning emailing... find a daffodil in the garden; craft a funnel vase with some color section of the newspaper; and stealthily deliver it to a co-workers desk to put a smile on their face.
That whole doorbell ringing thing? You're on your own for that.
Happy May Day!