• Download the SDK from ESRI's website http://resources.arcgis.com/content/geodatabases/10.0/file-gdb-api
• Extract the SDK, and put the contents of the directory in a known location, I used ~/local/filegdb. Here's an example path to one of the files: ~/local/filegdb/lib/libFileGDBAPI.dylib
• I use ~/local/filegdb so it can stay isolated in it's own place, you can put it anywhere, but the next few steps might be different
• Go into the directory containing the FileGDB SDK, e.g. ~/local/filegdb
• ESRI built these dylib's using @rpath's, so to avoid needing to mess with DYLD_LIBRARY_PATH, I updated the @rpath's using install_name_tool
• Here are the commands I used to patch the dylibs, this is not required if you want to use DYLD_LIBRARY_PATH yourself:

    install_name_tool -id "$(pwd)/lib/libFileGDBAPI.dylib" ./lib/libFileGDBAPI.dylib
    install_name_tool -change "@rpath/libfgdbunixrtl.dylib" "$(pwd)/lib/libfgdbunixrtl.dylib" ./lib/libFileGDBAPI.dylib
    install_name_tool -id "$(pwd)/lib/libfgdbunixrtl.dylib" ./lib/libfgdbunixrtl.dylib

• To verify the paths, use otool -L lib/libFileGDBAPI.dylib and otool -L lib/libfgdbunixrtl.dylib and make sure the paths are correct
• We need to make some changes to the configure.in script for GDAL now, since the FileGDB config code hasn't yet been updated for the OSX FileGDB SDK
• In the GDAL source root, edit the configure.in and replace it with https://gist.github.com/2005082
• In the GDAL source root, run ./autogen.sh to re-create the configure script
• Now run the configure script ./configure --with-fgdb=/Users/zacmcc/local/filegdb
• The configure script has many options, here is the configure line I use for my custom build: https://gist.github.com/2005091, if you have other GDAL builds on your machine (e.g. homebrew) that you don't want to interfere with, I recommend at least using --prefix=~/local or some other place on your machine besides /usr/local (default for homebrew) or /opt/local (default for MacPorts).
• If it worked properly, you should see in the output of configure indicating yes for FileGDB support
• make && make install
• If everything worked, it's time to test it out! Here's a test file: http://trac.osgeo.org/gdal/raw-attachment/wiki/FileGDB/test_fgdb.gdb.zip

    which ogr2ogr        # make sure it's the correct ogr2ogr first
    ogrinfo --formats    # list out the formats
    ogrinfo ~/Downloads/test_fgdb.gdb
    
    #convert FileGDB directly to PostGIS
    ogr2ogr -f "PostgreSQL" PG:"dbname='somedatabase' host='localhost' port='5432'" ~/Downloads/test_fgdb.gdb