How Can I get Google Natives apps in Samsung Galaxy S?
Installing from Market is preferrable, but you probably can sideload them if you exhausted all other avenues.

Download the apk: http://forum.samdroid.net/f10/google-updates-3468/

If you have adb, then you can install the apk using adb install.

If you don't have adb, then save those apks to the SD card and use a file manager (e.g. Astro, Estrongs, etc) to install them.

You need to enable non-Market installation: Settings > Applications > Unknown sources