The PSAs

DC ran PSAs (Public Service Announcements or Ads) in their magazines for many years. I'm not sure exactly when they started but it appears that they ended around July 1967; I was unable to locate any in Silver Age comics dated August 1967 or later (although I remember that DC had a similar series of ads in the 1970s called "Justice for All Includes Children"). But up until then, they appeared in almost every comic book DC published, with only occasional exceptions.

They were mostly pushed the "Be A Good Citizen" message, although some were geared at self-improvement, or safety, or family life. Here's a pretty good example:

I did some research on these over the last few days. The PSAs were very organized, to the point where you could probably identify the month of publication of a comic missing the outer wraps just by checking what PSA appeared in it. The monthly and eight times a year magazines all had the same PSA based on the cover date, while the bi-monthly mags all had PSAs based on the month prior to the cover date (i.e., Oct-Nov 1963 magazines would have a November cover date and the October 1963 PSAs, while Nov-Dec 1963s would have a December cover and the November 1963 ad). There was, however, one big exception: None of the romance comics published by DC carried the ads. My guess is that DC felt the readership of their love mags would be turned off by the ads, which were mostly aimed at young boys.

Some of the PSAs featured DC characters, such as Superman and Batman. DC's teen characters Buzzy and Binky popped up in quite a few ads, and as the series based on those characters had often ended years before it was often puzzling to readers. Just who was this kid Allergy? And why was Wolfie such a nasty little weasel?

Paulette Breen, the winner of a beauty pageant held annually at Palisades Amusement Park (a longtime DC advertiser) appeared in this one:

That appeared in October 1964, shortly after the Surgeon General's Warning first started appearing on cigarette packs. Hence the bit about adults not knowing any better.

The Health Myths Debunked ad convinced me to get a tetanus shot after I stepped on a nail one time. Some of the ads appeared more than once. According to several sources, the ads were written by longtime DC editor Jack Schiff and drawn by Bob Kane's ghost on Batman, Sheldon Moldoff.

Only one PSA that I was able to locate had text-only; this was the Big Dance, which appeared in many DC magazines in September 1956. It's about two teenage girls, who are bummed out that their parents have set a curfew for them to be home. To their surprise, they learn that their boyfriends (apparently a year or two older) also have a time limit.

I was able to assemble a list of almost all the PSAs published by DC from 1955 onwards using this list as a starting point, although a few proved elusive:

Jan 1955
Feb 1955 Binky's Special Christmas Quiz: Christmas in Many Lands
Mar 1955 Your United Nations at Work
Apr 1955 Peter Porkchops Don't Be Afraid to Speak Up
May 1955 Binky Gives Tips on Camping
Jun 1955 Buzzy There May Be a Career In Health For You
Jul 1955 Binky Gives Tips on Camping
Aug 1955 Buzzy Never Underestimate a New Idea
Sep 1955
Oct 1955 Buzzy Asks What Are You Getting Out of School
Nov 1955 Buzzy Do You Know Your Neighbors
Dec 1955 How a Nation Is Born Your United Nations at Work
Jan 1956 Binky in the Best Present of All
Feb 1956 Buzzy Asks Do You Know How to be a Good Babysitter
Mar 1956 Binky Healthy Teeth for You and Your Pet
Apr 1956 Binky Says It's Fun to Belong
May 1956 Get Your Ticket to the Treasury of Books
Jun 1956 Binky Presents Pioneers of 1776
Jul 1956 Do It Yourself Safety Rules
Aug 1956 Peter Porkchops Solves the Case of the Careless Camper
Sept 1956 The Big Dance
Oct 1956 Binky Shows How to Spend a Summer Week
Nov 1956 Binky's Special Election Exhibit
Dec 1956 Gifts to the United Nations
Jan 1957 Buzzy's Famous Books Quiz
Feb 1957 Winter Sports Champions of the World
Mar 1957 Buzzy's Special Brotherhood Week Quiz
Apr 1957 Buzzy Learns about Careers in Nursing
May 1957 A Date With Effie
Jun 1957 Worldwide Adventures in Science
Jul 1957 Binky Shows How to Make New Friends
Aug 1957 Earn While You Learn!
Sep 1957 Danger Prejudice at Work
Oct 1957 How Not to Enjoy a Vacation
Nov 1957 Teddy Roosevelt Guardian of Nature
Dec 1957 The Trick is to Treat All the World's Children
Jan 1958 Wanted: A Teen-Age Code
Feb 1958 The Flushing Remonstrance
Mar 1958 Do You Know What's Behind a Law?
Apr 1958 Peter Porkchops in the Secret of the Happy Pig
May 1958 Buzzy Scoffs at that Deep, Dark Secret
Jun 1958 Nature's Prize Pupil
Jul 1958 Are You a Litterbug?
Aug 1958 Wanted: A Pal
Sep 1958 Know Your Pet
Oct 1958 Binky: Lost--A Free Education
Nov 1958 Look to the Stars
Dec 1958 Sharing--the United Nations Way
Jan 1959 Formula for Success
Feb 1959 The Magic Card
Mar 1959 The Family Favorite
Apr 1959 What's Your BQ (Brotherhood Quotient)
May 1959 Do You Make Life Hard for Yourself
Jun 1959 Fred Finds a Way
Jul 1959 Buzzy Says Be Sure of Your Facts
Aug 1959 Peter Porkchops Gives Tips on Summer Fun
Sep 1959 Water: A Friend or Deadly Enemy
Oct 1959 It's Fun to Learn
Nov 1959 New Stars for Old Glory
Dec 1959 The Atom Servant of Man
Jan 1960 Binky in the Best Present of All
Feb 1960 Superboy Says It's Fun to Help Others
Mar 1960 Buzzy's Famous Books Quiz
Apr 1960 Aloha Hawaii
May 1960 What's Wrong with These Pictures?
Jun 1960 Be Your Own Boss
Jul 1960 Buzzy Says Free Speech Free for All
Aug 1960 Superman Lend a Friendly Hand
Sep 1960 Bike Safety=Bike Fun
Oct 1960 How Are Your Shopping Manners
Nov 1960 Keep Learning the Key to Success
Dec 1960 Children of Tomorrow
Jan 1961 Get a Grip on Your Gripes
Feb 1961 Our American Heritage
Mar 1961 Don't Sell Nature Short
Apr 1961 A Salute to Our American Indians
May 1961 How's Your Eye-Q?
Jun 1961 Parents Have Rights Too
Jul 1961 Gifts from Your Elders
Aug 1961 It’s Fun to Serve
Sep 1961 The Right to Be Different
Oct 1961 A Message from Otto the Robot
Nov 1961 Wanted: Safe Bus Riders
Dec 1961 People Are People
Jan 1962 Peter Porkchops in the Secret of the Happy Pig
Feb 1962 Let Science Serve You
Mar 1962 From Many Lands
Apr 1962 Do You Know Your Neighbors?
May 1962 Time Out for Talk
Jun 1962 Your Pass to New Worlds
Jul 1962 Superman Says Be A Good Citizen
Aug 1962 Not Wanted: High School Dropouts
Sep 1962 Buzzy's Rules of Water Safety
Oct 1962 Nature's Prize Pupil
Nov 1962 Health Myths Debunked
Dec 1962 Superman Talks about Pennies for Unicef
Jan 1963 Touchdown for Picasso
Feb 1963 Health Myths Debunked
Mar 1963 Safety First: All Year
Apr 1963 Salute to Our Fellow Citizens of Puerto Rico
May 1963 Countdown on Excellence
Jun 1963 Not Wanted: High School Dropouts
Jul 1963 A Tree Grow on Second Street
Aug 1963 How Not to Enjoy a Vacation
Sep 1963 Binky Shows How to Spend a Summer Week
Oct 1963 Play It Safe
Nov 1963 Your United Nations at Work
Dec 1963 Your Free Trip Around the World
Jan 1964 You Get What You Vote For
Feb 1964 Christmas in Many Lands
Mar 1964 Give and Take
Apr 1964 The Golden Rule
May 1964 Names Do Hurt
Jun 1964 Are You a Good Neighbor?
Jul 1964 Learn From Your Hobbies
Aug 1964 Rx Against Accidents
Sep 1964
Oct 1964 Smoking is for Squares
Nov 1964 Honesty is the Best Policy
Dec 1964 Children of Tomorrow
Jan 1965 Salute to Courage
Feb 1965 Superboy Says Don't Give Fire a Place to Start
Mar 1965 Friends Across the Seas
Apr 1965 Are You a Silent Witness?
May 1965 What's Wrong with These Pictures?
Jun 1965 Happy Hobby Time
Jul 1965 Binky Shows How to Make New Friends
Aug 1965 Summer At Home Can Be Fun
Sep 1965 Nature's Bill of Rights
Oct 1965 Are You a Litterbug?
Nov 1965 The Hip Way To Learn
Dec 1965 Builders of the Future
Jan 1966 The Magic Card
Feb 1966 The Invisible Handicap
Mar 1966 Do You Make Life Hard for Yourself
Apr 1966 What's Your BQ (Brotherhood Quotient)
May 1966 Health Myths Debunked
Jun 1966 Your Free Trip Around the World
Jul 1966 Natural Beauty--Everybody's Right
Aug 1966 The Policeman is Your Friend
Sep 1966 Get Hip to Old Folks
Oct 1966
Nov 1966 Lost: A Free Education
Dec 1966 Superman Talks about Pennies for Unicef
Jan 1967 Champs Against Odds
Feb 1967 Peace on Earth
Mar 1967 Countdown on Excellence
Apr 1967
May 1967 BEM Shows Up
Jun 1967 Mystery of the Million-Dollar Briefcase
Jul 1967 Make Your Summer Count

Favorites? I think everybody loved BEM:

I also liked How Not to Enjoy a Vacation, with the family pet describing the misadventures his owners had on a summer trip, and Honesty is the Best Policy, about three boys who find a wallet in a phone booth.

As far as I know, none of the other comics publishers did anything similar during the Silver Age.

Update: More discussion of the PSAs here.