Students can easily download a document from Edmodo, use it in another app (like a PDF annotation app) and then upload it again onto Edmodo to submit it as an 'assignment'. This solves the whole 'work-flow' problem that many teachers faced upon the introduction of iPads into the classroom. Worksheets, handouts, task sheets, graphic organizers, anything you want the students to work on, just upload it into your library, add it to a folder that you share with the students or attach it to a post, then they access it and open it in another app. Once they have finished, they need to upload it into their 'backpacks' and then submit it as an attachment to an 'assignment' that you posted.
Some free courses to learn about pbWorks, Edmodo, voice threads and more. It uses camtasia to slice video into segments so that you can watch at your own time.
I heart Edmodo coz it allows you to embed other web 2.0 tools like voicethread! I also find it user-friendly and a reasonable replacement for an LMS.
Strangely because it's micro-blogging, ppl associate it with twitter but I agree, its very much like FB!