1. Dropbox (www.dropbox.com): Dropbox gives users 2 GB of storage space for free. Dropbox allows users to setup shared folders as well. Dropbox also provides a small software piece that allows easy syncing from your computer to the web.
2. Box.net (www.box.net) Box.net give users 5GB of storage space for free. It also allows user to share folders and files fairly easy. However files must be uploaded through the website. Users can also drag files to the box.net page for easy upload.
3. Google Drive(http://drive.google.com Google Drive is a new service offered by Google that gives users 5GB of free space. It also works nicely with Google Docs as well as other files. Along with these sites there are sites such as Edmodo and Moodle that also allow students to upload completed work! So when the files are piling up, try a web based version of a thumb drive.