If your school does not have a learning management system, or maybe you are looking to supplement what you already have, here are some great places to go.
If you school does not have a learning management system, or if you are unhappy with the one you do have, check out Edmodo. This Facebook style site gives you the ability to write notes, assign assignments, quizzes or polls to all your classes or specific ones.
Not traditionally an LMS system, I have used LiveBinder as an LMS at my former school. It is a great way to deliver content and you can use it as a virtual binder for your students. Check out my videos on LiveBinder for more information.