Try this:
<?php
// starts or continues the session
session_start();
// set the value of a variable
// (you could just as easily grab it from
// form input or whatever)
$username = "somebaldguy";
// register the username to the session
session_register('username');
?>
...then on another page...
<?php
// starts or continues the session
session_start();
// echo out the value of $username
echo "$username";
?>
Now admittedly, this is a rather useless example, but it shows how to register a session variable, and then pull it back out, which is what you are looking for, I think (I could be wrong though =) )
-b3