wEdmodo is a fantastic site that my wife shared with me. I showed it to some of my fellow teachers and it is spreading like wildfire. Edmodo allows you to post assignments and collect online. It also a feature that allows you to send alerts out to your students' email and cell phones. This is great for reminding them about a test, field trip, or project due date. It has its downsides. I frequently run in to problems downloading files from the site that either I, or my students, have uploaded. Overall a great tool, but be prepared for some frustrating moments when you need to access a file.