Find a penny, pick it up, and
all day long you'll have good luck.
Earlier I shared a poster for the version found in English Proverbs and Proverbial Phrases by William Carew Hazlitt (GoogleBooks): Find a pin pick it up; all the day you'll have good luck. The version with the "pin" is also included in the Oxford Dictionary of Proverbs, edited by Jennifer Speaker. Although the ODP reports on contemporary usage, it does not report a usage that I have heard: "Find a penny, pick it up, and all day long you'll have good luck." Given that people are much more likely nowadays to find a penny lying around than a pin, I am not surprised by this usage, and the "penny" version is reported in the Wikipedia article on the penny.
The poster is made with AutoMotivator. The image is by miguelb at Flickr.