Back in 2000/2001, when seven of my books were released within a two-year period, I prepared a lot of promotional/marketing material. Too much, actually, but at the time I managed a prepress company and, though connections, had access to deeply discounted printing. I made folders and posters and postcards and bookmarks. I also created a series of business card-sized promotional pieces for each of five of the books.
Alas, much of that stuff remains in my office.
My mailbox is filled nearly every day with junk mail I neither request nor desire. Much of it contains postage paid returned envelopes. Until recently, I just threw the junk mail away.
About a month ago, I started doing something different. Before discarding the junk mail, I remove the postage paid envelopes. Once each week, I stuff two business card-sized promotional pieces into each envelope and drop the envelopes in the mail.
There is an infinitesimally small chance that someone on the receiving end will do anything more than throw the cards away. On the other hand:
a) I slowly reduce the pile of otherwise unusable promotional material in my office without the heartbreak of actually throwing it away.
b) I produce a small, but steady, flow of business for the USPS, an organization that has faithfully delivered my manuscripts to editors in good times and bad.
c) I make companies that waste my time with junk mail spend a few fractions of a cent, thereby "sticking it to the man" in my own subtle way.
d) I just might sell a book, and that would be one sale I never would have had otherwise.