Unpivoting your data means grabbing a data series from buckets across the columns of your data source (usually a spreadsheet) and transposing along the rows instead. This can be accomplished with a wide variety of tools, however two will be covered here, T-SQL and the Data Explorer plugin for Excel 2013.
The TQL Example is provided below using a sample dataset that has the Year pivoted in 3 columns, 1 column for each year in the dataset, 2004, 2008 and 2012. We UNPIVOT these years into two values, a year and the value for that year. The year we call [Years] and the value we call [Medals] :
CREATE TABLE [dbo].[SomeData](
[Country] [varchar](20) NULL,
[Sport] [varchar](20) NULL,
 [int] NULL,
 [int] NULL,
 [int] NULL
) ON [PRIMARY]
INSERT [dbo].[SomeData] ([Country], [Sport], , , ) VALUES (N'Australia', N'100m Womens', 14, 12, 3)
INSERT [dbo].[SomeData] ([Country], [Sport], , , ) VALUES (N'Somalia', N'100m Womens', 0, 0, 0)
SELECT Country, Sport, Years, Medals
FROM [dbo].[SomeData] Main
[Medals] FOR Years IN (
Another alternative is to utilise the latest release of the Data Explorer plug-in for Excel 2013. This could make a lot of sense, give that your pivoted data source could be in Excel anyway. You can find a link to the latest release of Data Explorer containing the Unpivot feature here http://blogs.msdn.com/b/dataexplorer/archive/2013/04/12/download-the-latest-data-explorer-update-unpivot-feature-and-search-experience-improvements.aspx.