CNN leans noticably, but still relatively lightly, to the left. They seem like they try to remain relatively unbiased, but the natural tendancy of most of their anchors, strong personality opinion people, and producers seems to be left so it shows through.
FOX is noticably and decidingly right slanted, with MSNBC being their mirror on the left.
Both FOX AND MSNBC seem to be obviously catering to one side or the other while CNN is trying to play it down the middle, or what they view as the middle which is generally left leaning, as best as possible.
No, I don't think any of these are "propoganda" arms of a political party. I do think political propoganda in certain ways show up on all three, and as someone pointed out shows up in non-news, non-political TV entities as well (IE normal shows).