BBC
Reuters
Guardian
Talkboards acting as early warning systems, as someone said upthread.
Miscellaneous.

At least as important as the sources is having learnt about the mass media to know something of how they work and how to evaluate them.

I did this via interests in communication itself, politics, economics, philosophy, sociology and psychotherapy. That last is useful for things like cognitive dissonance, which helps to explain why people can't see what's right infrot of them sometimes. The psychotherapy was also useful for understanding my own biases. That list of subjects gives me a framework for trying to understand what goes on.

Miscellaneous includes things like the prog now on Beeb radio 4 "U.K.Confidential 1981", a first look at the government documents released now under the 30-year rule.

In it we learn e.g. that when Thatcher said "We don't negotiate with the IRA cos they are criminals", she and her government were actually doing just that - negotiating. Thus, by extension, we can see that when democratic governments make definite assertions, that is not proof that they are telling the truth.