Time Management in the Classroom

A frequent conversation I have with my co-op is the idea of not having enough time in a period to complete what we want to do. I often get caught up in the mindset that English is the only thing my students need to know, and they should spend all day with me, however, I'm quickly brought back to reality and realize that all of the other subjects are probably thinking the same thing. So, no matter how much I wish, or complain, or get frustrated about it, there's still only 40 minutes in a class period, and I have to do with it what I can. However, sometimes I feel like all of the great stuff we learn in class could never be possible in a classroom when there is only 40 minutes. For example, it would be great to do a free write with my students for 5-10 minutes everyday, but at the end of the week, that's 1/5 of the class time that week that could have been used for something else. Even when planning my unit, I felt like I had to leave out so much stuff, because there is only so much time within the year that I have. I could probably talk about about this for a very long time, but I'm sure you all understand. So I guess my real question for you all is how are you handling time management in your classroom? How much more do you think you could accomplish if you had more time? What kinds of things would you love to do in your classroom, but you don't have the time for?