Back in 2010 we had the same problem and i successfully employed GoogleDocs with our small Agile Development team (8 Devs in 3 Countries).
GoogleDrawing will serve in the exact same way as a physical Scrum board would, with all the upsides of full flexibilty and also the downsides of zero automation but with the big additional upside of being virtual and accessible from anywhere with an internet connection.
It also was used for the retrospective at the end of each Sprint
GoogleSpreadsheet was used for a concise list of all the tickets from our bug tracking system (Redmine, manually transfered) and also for the (manually updated, albeit with formulas to calculate the progress) burndown chart.
The combination of these different elements is actually quite powerful, as you have the full flexibility over the content and its representation and can have your team communicate via VoIP while all are looking at the same documents and can modify them in real-time.
Here an example of the docs used in a sprint (all sensitive data removed):
- Scrum board Example (GoogleDrawing)
- Retrospective Example (GoogleDrawing)
- Burndown Chart Example (GoogleSheet, formulas to automate calculation)
- Ticket list from Bugtracker (GoogleSheet)
As mentioned before, the only downside is the fact that you have to invest some time to maintain and prepare the data for each sprint, but for us that was hugely outweighed by the flexibility and accessibility that the Team of GoogleDocs + VoIP gave us.