result = GetGoogleSpreadsheet(DOCID)
[DOCID] A value like '0AmQ013fj5234gSXFAWLK1REgwRW02hsd3c', which is found in your spreadsheet's url:https://docs.google.com/spreadsheets/d//edit#gid=0.

[result] cell array of the the values in the spreadsheet

IMPORTANT: The spreadsheet must be shared with the "anyone with the link" option.

This has no error handling and has not been extensively tested.
Please report issues in comments below.

Thanks to @MarkTomaszewski and @Constantine for noting the updated url format (the above description has been updated to reflect this).