You don't have to download any software to use these tools. These are similar to a wiki, but you need a password to view the document, as well as to edit it.
I used Zoho Writer last year with my DI team. They could work on different parts of their planning and script from any internet connected computer. They have lots of other tools, too.
Google also has a group of online tools, including documents.
Another way to create useful online documents