I want to articulate the fundamental ideological planks of what I see as the progressive movement.
Humanism: I think the fundamental value of the progressive movement is to value that which promotes human happiness and diminishes human suffering. This plank stands in stark and principled contrast to the conservative movement's value of adherence to abstract ideals. To a progressive, an ideal is worthy not in itself but only if it promotes subjective human well-being. To a conservative, one should adhere to the ideal for itself, even if it doesn't promote subjective well-being in reality.
Libertarianism No, not like the "Libertarian" party, which is no more libertarian than the "Republican" party with its king is about a republic, or the "Democratic" party, which ignores and challenges the principles of its voters, is about democracy.
I mean "libertarian" in the sense of valuing personal liberty and, insofar as practically possible, freedom of choice. Libertarianism entails that, while there are some wrong ways to live (e.g. as a criminal or in poverty), there is no "One Right Way" to live.
Communitarianism: The idea that we have positive moral duties to each other. We have a duty to promote happiness and relieve unnecessary and unchosen suffering in our fellow human beings. The "Invisible Hand" cannot regulate everything (or, in another sense, we should recognize that the Invisible Hand regulates not only economics but also politics: i.e. "There ain't no such thing as governnment interference").
There is a certain dynamic tension in these positions. Humanism has internal tension: the happiness of one person can entail the suffering of another. The essence of progressivism, though, is that we resolve these difficulties not by appeal to an abstract ideal, but rather by getting down into the gory details and figuring out how precisely we have the best effect on human well-being.
Libertarianism and Communitarianism are also in tension. We have a communitarian duty to others so long as we're not interfering with their own choices: No one is substantially interfering with my freedom of choice, for example, by making it impossible to live in involuntary poverty, but one might well object if our government forces her to quit smoking.
Progressivism, unlike conservatism, does not provide simple, easy answers. This is a feature of progressivism, not a "bug".
The only way conservatism can provide its simple, easy answers is by promoting as its highest meta-value submission to authority: Submission to the unquestionable authority of church and religion, to political leaders, and to objective moral virtues. The problem with the meta-value of submission to authority is that there's never only one authority; and once you submit to some authority, you cannot negotiate--you can only fight.
By explicitly embracing complexity and tension, progressive ideology preserves its ability to negotiate without sacrificing a strong principled position from which to negotiate.
All of the terms which I used to label these planks have been corrupted and redefined by opponents to a greater or lesser degree. Better rhetoricians, polemicists and politicians than I will doubtlessly have to present these planks in a more salable fashion.