Victor,
>I came to this wonderful freeware program shp2kml, which converts maps in ESRI/SHP format to KML and then displays them in Google Earth. Amazing stuff.
>I'd like to integrate it into my application, but the sad thing is that the program is a standard exe with no command line options and no API or any other interface.

Google Earth and other programs can usually be handled through their own API's/WS-Interfaces.
AFAIR Google has 50 calls free per day - others are similar or give you Implementations including Apache and their WS for a localhost-testing install. Might be relevant to get call count/price range info beforehand <bg>.

regards

thomas