Leo Babauta at Web Worker Daily has posted a very thorough guide to working virtually that focuses primarily on tools but also includes some excellent workflow recommendations. It's a bit Google-centric but he does provide a number of alternative choices for most of the key ingredients for a cloud-based workspace.
What is apparent in reading his article and increasingly is impacting the decisions I make about the web-based tools I use is how, over time, the integration and interaction Google is building into their individual offerings is feeling more and more like what Microsoft has done with Windows, Office, and Internet Explorer. Or, on the other side of the aisle, how Apple has, with the assistance of some really talented third parties, managed the same on OS X with iLife and iWork.
It really is beginning to come down to a three-way horse race between Microsoft, Apple, and Google to determine who delivers your workspace. The first two are, quite obviously, impacted by hardware choices and preferences. Google is agnostic and actually is the best way to work on both platforms with relative ease (assuming you have the budget and need to use both a Windows PC and a Mac).
If you're using Linux, Google is the clear leader, especially as integration with popular tools like Evolution and OpenOffice continue to emerge.
Platform independent RIAs will further blur the lines. With the recent introductions of the Apollo alpha from Adobe, Silverlight and Popfly betas from Microsoft, and Google Gears, the shape of the connected world we're moving into is becoming clearer all the time.