From within the Tabulaw site, you can search for a court opinion. (It uses Google Scholar to find cases.) Once you find a case, as you read through it, you can highlight passages. The text you highlight is automatically saved, complete with its citation. The passages are saved in Quote Bundles to which you can assign names and descriptions.
Once you have done your research and you are ready to start writing, you can do that from within Tabulaw also. You can create and edit a new document in Tabulaw, upload one from your computer, or import one from Google Docs. It appears that Tabulaw uses Google Docs as its document-editing base.
As you write, your quotes are displayed in a panel to the right of the document. Simply click any quote to insert it in your document, complete with its full citation (including page citation). You can also click a button to return to the case and see the quote in context. Any documents you create in Tabulaw can be downloaded to Microsoft Word.
Tabulaw has fairly rudimentary collaboration features at this point. You can share your Quote Bundles with other Tabulaw users or send them by email. You cannot share documents directly from within Tabulaw, as far as I could see.