Maybe not slang as much as a slogan:
Ass, cash or grass. No one rides for free.
A popular bumper sticker of the times.
Slang:
Outta sight (man)
Lay it on me - give me some skin. A way to greet others and slap five, not a high five.
You’re blowin’ my head man or you’re bringing me down man
Let’s get faced (meaning go smoke a joint)
Uptight
Far out
Right on
Peace (typically with a gesture of a V with fingers)
Later (a way to say goodbye)