Logged in user ID as post ID

You can get information on the currently logged in user using the get_currentuserinfo() function.

For example:

<?php
  global $current_user;
  get_currentuserinfo();
  $username = $current_user->user_login;
  $user_id = $current_user->ID;
?>

You can then use $username or $user_id in your custom loop.

<?php 
   // assign the variable as current category
   $category = $user_id;

  // concatenate the query
  $args="cat=" . $category;

  // run the query
  query_posts( $args );

  if ( have_posts() ) : while ( have_posts() ) : the_post(); 

 // do something here

 endwhile;

 endif;
 wp_reset_query(); 
?>