Creative Marketing - and partial photo success!

I finally figured out how to install my photos myself! (But the PhotoShop make-it-look-good technicalities are still pending...Bob turned the photo of me and my great-nephew right side up, but you'll have to tip your head for the one of my sister. I downloaded it all by myself! Yay-uh!)
So, I was at the County Fair painting faces next to a soldier booth raffling a rifle for money to send to troops. They were doing a fine business. One of the guys in uniform asked if I would give part of my face painting money to the soldiers if they sent business my way. Sure! So every person he talked to was directed toward my booth. Sweet! I gave a dollar out of five for each face painting from the soldier booth. That was creative of him, and it worked for me, too. It made me ponder on ways I could piggyback with other businesses to sell more books. Captivating thinking!
What piggyback marketing ideas have you come across?