cheat sheets.

European Petroleum Survey Group projection codes cheat sheet for Dayne

http://spatialreference.org/

EPSG:4326   - WGS84 (Geographic) # that default one that haunts you
EPSG:3338   - Alaskan Albers NAD83
EPSG:900913 - Google's web mercator
EPSG:3857   - *USE THIS* Official EPSG for Spherical Mercator 
            |- Google/Bing equivalent
EPSG:3785   - *DEPRECATED* Spherical Mercator
EPSG:102100 - ESRI's web mercator (WGS 1984 Web Mercator - Auxillary Sphere) 
            |- Google/Bing equivalent
            |- ArcGIS 9.4+ will switch to EPSG:3857 (http://forums.esri.com/Thread.asp?c=93&f=984&t=288607)
EPSG:102113 - *DEPRECATED* ESRI web mercator projection