Political freedom and political liberty are similar. Liberty of course stemming from the Latin libertas, which just means freedom. If you don't put political in front of these two words you're looking at what LaVaughn described. Liberty is a bit more hefty, feeling more like an entire group of people or subgroup, just larger than yourself. Now freedom feels a bit more lightweight. My freedom is that I can go and smoke a big fat cigar right here on my own porch, I'm free to do that. And of course sometimes it just happen to be part of a set phrase: I'm not at liberty to divulge this information.

I think of liberty as being free from despotic (bad) government or control, although there are other meanings, as well. Freedom is personal independence. It also can mean not being confined. Hope this helps! :-)