Currently:
The News Hour with Jim Lehrer (to tell me what's going on),
NOW, with Bill Moyers (to tell me what's really going on),
Masterpiece Theatre (to blow a little clean air through my head),
Everybody Loves Raymond (to show me that life—no matter how dysfunctional—goes on),
The Red Green Show (to keep life in perspective).

A few from the past:
Northern Exposure, The Rockford Files, Mystery, Family, Babylon 5, Blake's 7.
All incarnations of Star Trek (currently watching Enterprise, but I keep thinking, "Gene Roddenberry, we need you back!")
As Time Goes By
Good Neighbors (The Good Life in the UK)
Waiting for God
(the last three Britcoms, we watch re-runs whenever they're on)

Don Firth