I don't know about sites, I am sure there are many, but if you really want to learn about it, I think one of the best albums to listen to would be the sountrack to "Hair" the musical. (better yet, see the musical if you can) I think it pretty much sums up the hippie era of the 60's.
They made a movie in the late 70's, but it wasn't near as good and left out a bunch of the good songs.
You might can try looking for "The Summer of Love" on a website.
Some good hippie movies from the 60's would be "Alice's Restaurant", and "Easy Rider". Also the "Yellow Submarine" movie was a good psychedelic one.
Bob Dylan and Grateful Dead were popular figures in the hippie era, and Psychedelic Rock as well as. Sgt. Pepper was a good hippie album.
You might can look up protest songs, flower power, Haight Ashbury Park, etc, in the search bar.
