A new update for Office Live Workspace appeared on the Microsoft Download Center today (thanks Alex for the tip!).  The update, version 1.2, published 8/12/2008, includes:

(1) performance updates to make using Office Live Workspace with Microsoft Office programs faster, (2) the latest Office Live Add-in for Microsoft Office that enables you to access your workspaces directly from Word, Excel, and PowerPoint and (3) the Multiple Document Upload Tool and (4) the Firefox add-in to allow users of the Firefox browser to use Office Live Workspace with Microsoft Office.

The last update (version 1.1) included the Multiple Document Upload Tool, but apparently the Firefox support is new to this update.   The Office Live Workspace beta offers 500mb of online storage available through the Office Live Add-in to Office XP or Office 2003 (via a toolbar), or Office 2007 (via new menu options).  The Workspace can be shared, and/or accessed through a web interface.  You can learn more about Office Live Workspace on the homepage.