Oh my goodness - there are so many!
Others have listed Happy Days, Laverne and Shirley and the classic comedies like Lucy.
I haven't seen some of my favorites:
Mary Tyler Moore
Quincy
Rockford Files
Magnum PI
Simon and Simon
Riptide
A-Team
and my favorite show ever - Emergency!
I watch many of these on TV Land and RTN and even Hulu. Yes, sometimes they were corny, and the 70's fashions were pretty bad, but there is an innocence about some of these that you can't get anymore. I think that is why I like the current show Chuck so much, it reminds me of the old stuff.
BTW I've heard that there is a rumor that Rockford is being brought back but I don't see how they can ever cast anyone as well as James Garner for Jim Rockford. I don't think that I'd watch it.