Like you, I'm liberal, atheist, feminist and pro-choice, and my thought is this. My kids can believe what they want to - for a while both kids believed in god and I was fine with that. The idea of a higher power seemed to comfort them. Why take that away? They'll grow up soon enough. What I DID make sure to do was to discuss in some detail the creation stories and beliefs of some of the major religions, as well as what scientists can tell us about important world events (the formation of the Earth, etc.). Once they have the facts, they start thinking critically all on their own. And although I find most religious beliefs to be absurd, I still teach my children that we would never, ever make fun of or let religious people know that we think that, because their beliefs are very important to them and it would hurt their feelings. (We're not evangelical atheists... LOL)
Anyhow - with regard to political beliefs, again, I arm them with facts. In my opinion, if you care about your fellow man, there's pretty much only one political view you can have, and if my children grow up to be socially conservative, I will definitely feel that I have failed them completely as a mother. That being said, we talk a LOT of politics in our household, and I try very hard to have fact-based discussions. In other words, we learn about history to see what has happened in the past, and then try to apply that to our current situation. Instead of taking a news organization's word for how facts should be interpreted, we try to find the facts from a neutral source and decide what that means for ourselves. Now - it should be said that I do not identify with one political party or another, but rather I have an ideology and then try to choose the candidate or ballot choice that best suits my way of thinking. (Although I DID buy "Ban Republican Marriage" shirts for myself and the kids when Prop 8 was on the ballot. Not apologizing for that one.)
To paraphrase one of my favorite comedians, Bill Maher, there are not ALWAYS two sides to every story. For instance, you're not obligated to present creationism along with the Big Bang Theory as two equally valid answers. Science deals in facts that lead to a logical theory (that in itself may not be 100% correct, but is probably a pretty darn good guess). Religious stories are stories, and should be taught as such, though they do provide a valuable sociological study of a society. As a parent, you're allowed, and SHOULD, help your kids make that distinction.
What a great question! I'm glad you asked it. I'll be eager to read the other responses.