Popular Well Known Text representations of Spatial Reference Systems

Here a some of the most common WKTs. See SRID.CSV in the release for more,

WGS 84 geographic coordinate system

GEOGCS["GCS_WGS_1984",
     DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137,298.257223563]],
     PRIMEM["Greenwich",0],
     UNIT["Degree",0.0174532925199433]
]

Universal Transverse Mercator - WGS84 based

This sample includes Authority numbers. These are not strictly necessary but good practice to include.

PROJCS["WGS 84 / UTM zone 32N",
     GEOGCS["WGS 84",
          DATUM["WGS_1984",
               SPHEROID["WGS 84",6378137,298.257223563,AUTHORITY["EPSG","7030"]],
               AUTHORITY["EPSG","6326"]
          ],
          PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],
          UNIT["degree",0.01745329251994328,AUTHORITY["EPSG","9122"]],
          AUTHORITY["EPSG","4326"]
     ],
     PROJECTION["Transverse_Mercator"],
     PARAMETER["latitude_of_origin",0],
     PARAMETER["central_meridian",9],
     PARAMETER["scale_factor",0.9996],
     PARAMETER["false_easting",500000],
     PARAMETER["false_northing",0],
     UNIT["metre",1,AUTHORITY["EPSG","9001"]],
     AUTHORITY["EPSG","32632"]
]

This example is for zone 32N. To create for other zones, change the following: central_meridian = ZoneNumber * 6 - 183 false_northing: 0 for North, 10000000 for South. Last EPSG number for projection = (32600 + Zone) and add 100 more if zone is south.

Microsoft Virtual Earth / Google Maps Mercator Projection

PROJCS["Popular Visualisation CRS / Mercator",
   GEOGCS["Popular Visualisation CRS",
      DATUM["Popular Visualisation Datum",
         SPHEROID["Popular Visualisation Sphere", 6378137, 0, AUTHORITY["EPSG",7059]],
         TOWGS84[0, 0, 0, 0, 0, 0, 0], AUTHORITY["EPSG",6055]
      ],
      PRIMEM["Greenwich", 0, AUTHORITY["EPSG", "8901"]],
      UNIT["degree", 0.0174532925199433, AUTHORITY["EPSG", "9102"]],
      AXIS["E", EAST],
      AXIS["N", NORTH],
      AUTHORITY["EPSG",4055]
   ],
   PROJECTION["Mercator"],
   PARAMETER["False_Easting", 0],
   PARAMETER["False_Northing", 0],
   PARAMETER["Central_Meridian", 0],
   PARAMETER["Latitude_of_origin", 0],
   UNIT["metre", 1, AUTHORITY["EPSG", "9001"]],
   AXIS["East", EAST],
   AXIS["North", NORTH],
   AUTHORITY["EPSG",3785]
]  

*Note that this is the projection they use for display, but geometry input/output is using WGS84 geographic.