Another interesting thing that I have been poking around at for some time is the ability to read ESRI Access Personal Geodatabases directly from their binary representation without the need for ArcObjects. The trickiest part of this was having to interpolate curves. I have this working to a reasonable degree.
The current prototype exports PGDB feature classes to KML, Shapefiles, and into SQL for importing GIS data into PostGIS, and has been tested with PGDBs created with ArcGIS 9.1 and 9.2. This opens more data for use with Shape2Earth.
I have been assuming that the same binary structure used in Access databases are also used by ArcSDE, but have not had the chance to test this theory out.
This same method could be used to create and edit Personal Geodatabase (and ArcSDE for that matter), but I doubt I’ll ever have the time to see this through.