Google Documents

You are able to create documents that can be shared with certain people, people who have been given the link or publish it on the internet for all to see. You can easily share your document with other people who have google docs by entering their email address in under the 'add people' heading. They can check their google docs account and see any shared documents and open it. You can also change the settings so people the document is either read-only or able to be edited.
When you can edit it you can see the changes as they happen so you don't need to refreash the page to see any updates.
By going to 'file' then 'see revision history' you can see who has made what changes to the document so if it is a group assignment you can see who is pulling their weight.
If you go 'file' then 'download as' you can download a copy of the document as a different file type such as PDF, Word or HTML.

It makes group work very easy as all you need is either a google account or the link to work on the document. It is also easy to email as an attachment. Just 'share' then 'email as attachment'. You don't have to just be stuck with documents but can also do presentations, spreadsheets, forms and drawings.
The upload limit is 1GB.For documents you can store around 100 pages. For presenations you can store around 200 slides.