Confused?!?!

ie. bluemarine.theme or xtemplate.theme (in cvs main) and set the variable ("center_content") to the blub you want to appear on the main page. you do latter by

1. adding $conf["center_content"] = "blub"; to your conf.php, or
2. putting it, in serialized form, directly into the "variable" database table, or
3. using dries' recent "theme settings" patch and set it directly from the admin area (patch for xtemplate.theme only)