How to make a posts page display only intros of posts?

Question

You need to go inside the code of your category.php and…

Change:

the_content(); //or similer

to:

the_excerpt();

Goog luck..

Revised Answer for twenty eleven theme:

1. Open content.php and search for this line:

<?php if ( is_search() ) : // Only display Excerpts for Search ?>

2. change it to this:

<?php if ( is_search() || is_category() || is_archive() ) : // Only display Excerpts for Search ?>

Hope this helps..
Best regards, Sagive.