AOPA's Passenger Safety Briefing Card
Not only a good idea, a safety briefing for all passengers is required by FAA regulations. AOPA has created a briefing card specifically for this purpose. Download and share it with your flying friends. Better yet, make a copy and incorporate it into your aircraft checklist.
Safety Alerts from the NTSB
The National Transportation Safety Board (NTSB) publishes Safety Alerts for aviation, as well as other modes of transportation. for their list of Aviation Safety Alerts. As a bonus, there are Safety Alerts for highway vehicles and for boating!
The NTSB is an independent federal agency charged by Congress with investigating every civil aviation accident in the U.S. and significant accidents in other modes of transportation-railroad, highway, marine and pipeline.
Their Safety Alerts make interesting reading - check them out!