I actually think speaking and listening overlap quite a lot. Whenever we're speaking or writing we're basically reproducing words, phrases and grammar constructions that we've heard used a thousand times before by others, that's the only reason we even know how to use them. If you've heard a term fifty times on the radio one day, it will pop into your head quite easily during a conversation the next day. I've been listening to a lot of French for the last several months and I've noticed improvements in my accent, vocabulary and grammar, even though I've made no conscious effort to improve my speaking.
However, I agree with Cainntear that listening is not enough. It will give you the materials to work with but then you need to know how to use and combine them to fluently phrase your own thoughts and that takes practice.
