You can create sites, usually for free, which allow you to communicate online with your students and to store files such as documents, PowerPoints, Videos and maps and images. These are great for students as they have access to all of the information whenever they need it. You can usually customise them to look the way that you want them to and can add in features such as customisable logos and pages.
The easiest one to set up is the one that you are reading now.

Wikispaces has free wikis for teachers ( and you can have several of them) where you can keep all of the information that you want your students to have. They have a discussion forum (the tab at the top of the page) and a history file which allows you to see who has uploaded what when.You can embed videos from sites like YouTube or Teacher Tube or your own videos.

Grouply is a site which uses the best of wikis and includes a blog for each user. It allows users to have their own pages and to communicate freely with other users by 'friending' them. It includes several widgets which you can add ,rearrange or delete . Currently the English department are using these for senior students as a way of encouraging discussion. They have live chat boards as well as forums.

Edmodo is an online web 2.0 site that encourages collaboration. It is closed and teachers can generate a unique code that only their students can use. They can share video, have discussions and chat securely.

Weebly is a blogging platform and website for teachers with an easy drag and drop interface which is very easy to use.