In order to take a screenshot you must:
1) Root? (TBD)
2) If it is determined the Galaxy S 4G must be rooted, read this great article as a workaround.
3) Programs used to capture screenshot (Root Required): ShootMe, drocap2
4) Please host pictures on a site such as Photobucket or Picasa, and then use the insert image tool above to add them to your post
If you use any cool and/or interesting theme's, homescreen replacements, or widgets, please list them in your post also.