srsly. I want one too.
Many people seem to look them up at http://spatialreference.org
When you import shapefiles using PostGIS (and the PostGIS loader for PGAdmin), it looks up the proj information in a table called spatial_ref_sys.
From what I understand, the standard spatial_ref_sys table packaged with PostGIS includes only OGC WKT (Open Geospatial Consortium Well Known Text) representations of some Spatial Reference Systems and NOT the ESRI Spatial reference systems.
From the PostGIS 1.5.2 documentation:
The spatial_ref_sys table is a PostGIS included and OGC compliant database table that lists over 3001 known spatial reference
systems and details needed to transform/reproject between them.
Although the PostGIS spatial_ref_sys table contains over 3000 of the more commonly used spatial reference system definitions
that can be handled by the proj library, it does not contain all known to man and you can even define your own custom projection
if you are familiar with proj4 constructs. Keep in mind that most spatial reference systems are regional and have no meaning
when used outside of the bounds they were intended for.
An excellent resource for finding spatial reference systems not defined in the core set is http://spatialreference.org/
Some of the more commonly used spatial reference systems are: 4326 - WGS 84 Long Lat, 4269 - NAD 83 Long Lat, 3395 -
WGS 84 World Mercator, 2163 - US National Atlas Equal Area, Spatial reference systems for each NAD 83, WGS 84 UTM
zone - UTM zones are one of the most ideal for measurement, but only cover 6-degree regions.
Various US state plane spatial reference systems (meter or feet based) - usually one or 2 exists per US state. Most of the meter
ones are in the core set, but many of the feet based ones or ESRI created ones you will need to pull from spatialreference.org.
However ogr2ogr contains ESRI spatial ref systems as a I recently learned through the generosity of others.
In both ogr2ogr and spatial_ref_sys, it seems that text contained in the .proj file is compared with a table of OGC WKT, which is a slightly different text format from the ESRI WKT format that you often find in a .proj file. Also, I'm not sure how PostGIS looks up each SRS, but the small differences between ESRI WKT and OGC WKT might result in failed matches.
It seems like it would be simple to attach ESRI spatial ref systems to the default spatial_ref_sys table in PostGIS. Maybe someone already has, with some patch or a script.
I could be wrong, because I've just been running into this for the past few days, and I've been frustrated with the same thing.
Maybe someone else knows a great resource?