Ask Mr. Smarty Plants

Sorry, but Mr. Smarty Plants doesn't know of any plant that will repel snakes.  You are not, however, the first person to ask this question—see the answer to a previous question.  Your best bet for avoiding snakes is to be ever watchful about where you step and put your hands and by modifying your habitat.  Make sure the vegetation around your house is open enough that you it doesn't provide hiding places for snakes or for the rodents that many of them like to eat. Keep your area clear of brush piles and keep your grass cut—a snake that you can see is a snake you can avoid.  The article "Reducing Snake Problems around Homes" from Mississippi State University has useful advice for identifying, excluding, and capturing unwanted serpents.

The USDA's Animal and Plant Health Inspection Services (APHIS) has formulated an effective snake repellent using cinnamon oil, clove oil or eugenol. This was developed for reducing the numbers of brown tree snakes near shipping ports on Gaum to minimize accidentally including them in shipments to the US.  There are also commercial snake repellents advertised that you can search for on the internet, but we do not know if they are effective.