These are two big hits I'm sure you must have heard:
Twilight Zone, 1982
When the Lady Smiles, 1984 (the video clip was too much for the USA though)
Back Home, 1970. Was their first hit and pretty known as well.
Enjoyable concert registrations on YouTube.
1975, San Francisco (USA) (during this time the band was expanded with some other musicians)
1982, Rockpalast (Germany)
Some favourite songs/albums of mine:
I recommend the whole
Eight Miles High (1969) album which features Sabbathish music, but also psychedelic.
And the whole
Golden Earring (1970) album as well.
She Flies on Strange Wings, 1971
Vanilla Queen, 1973 (probably my fav!!)
awesome live versions:
Sleepwalkin', 1976
This is their first live album,
Live (1977)
(might continue this later)