What Multiheaded said, basically. Generally speaking: for IP reform, for tax code simplicity, improving science curricula, against corporate subsides.
In my experience while progressives and leftists (is there a difference?) are in principle for tax code simplicity and against corporate subsides, they're also for the government making "smart investments in our future" which tend to look suspiciously like tax code loopholes and/or corporate subsidies.
As for improving science curricula I don't think the groups in question would agree on what an improved science curricula would look like, in particular a lot of libertarians would argue that government should get out of the business of setting school curricula entirely.
I was thinking about the hazards of bad government, and wondering if there was a way for the LW community to do something to oppose them, and it occurred to me that we might be picking up the problem by the wrong end.
The usual way of thinking about political action is to start with one's political identity (progressive, libertarian, whatever), and that's likely to put one at odds with people who have opposed identities.
Instead, I believe there are projects which could appeal to rationalists across a wide range of the political spectrum. A couple I can think of are opposing the war on drugs and improving judicial systems. Any other suggestions?