Before Captain Planet was even a thought in the mind of cable mogul Ted Turner, Woodsy Owl was teaching kids about the environment. I'm sure you remember the phrase, "Give a hoot, don't pollute!", from back in the day, right?
Anyway, Woodsy was introduced in 1965, but the above phrase wasn't added until 1971, and that's when the PSA's began airing. Four different actors, including Sterling Holloway (better known as the original voice of Winnie the Pooh), Barry Gordon (the Nestle Quik Bunny, among other credits), and Frank Welker, have spoken for Woodsy through the years. I'm not sure if it's either Holloway or Welker in this one from 1977:
In the 90's, Woodsy was given a radical makeover, but the commercials stopped airing, insofar as I know. In his prime, though, Woodsy transitioned to comic books, as a short-lived series was published by Gold Key in the mid-70's.