Is there any way to get uid from user name in Drupal?

The user load function is very heavy, would use up more resources and return more data than required, Here is a nice little function for you:

function get_uid($username)
{    
    // Function that returns the uid based on the username given
    $user = db_fetch_object(db_query("SELECT uid FROM users WHERE name=':username'", array(":username" => $username)));

    return $user->uid;
}

Note: This code is revised and input is escaped, so the code is not dangerous in any way.