Opendap handles transport, translation and subsetting of data. Opendap allows you to access remote data over the internet :

• using familiar data analysis and visualization packages like Matlab, Ferret, IDL,... as if the data were on your computer
• without worrying about data storage formats, translating them on-the-flight (including in ascii), if necessary
• accessing only the data of interest (extracting geographical area, time series...).

For example, to use directly Ssalto/Duacs merged near-real time sea level anomaly data (merged NRT-MSLA) with Ferret software :

• launch Ferret
• type : use "http://opendap.aviso.oceanobs.com/"     (see Aviso Opendap for the data http addresses)
• then "show data" shows the file characteristics.

Data are in "grid_0001". This grid includes all available msla_oer_merged_h data from the beginning (August 2001). "show grid grid_0001" returns number of points, beginning and end value, in longitude, latitude and time. grid_0001 can be used as a local data source; network access are completely transparents, and concern only selected data.
For more information, look at an exemple of command lines and of maps in a Lively Data: Direct access to the data behind the LAS

You thus can plot a map, a longitude-time diagram, etc. What can be done with Ferret is also possible with other "client" software like ncBrowse, IDL, Matlab... (see OpenDap website for the complete software list)

Have a look at Aviso Opendap