A pl/sql script to recompile all invalid objects in oracle. Simple but powerfull.

DECLARE

   obj_name_    User_Objects.object_name%TYPE;
   obj_type_    User_Objects.object_type%TYPE;
   str_run_     VARCHAR2(200);
   cid_         INTEGER;
   ret_         INTEGER;
   CURSOR Invalid_Objects_ IS
      SELECT object_name, object_type
      FROM user_objects
      WHERE status = 'INVALID'
      ORDER BY object_type ASC;

BEGIN 
   FOR Get_Rec_ IN Invalid_Objects_ LOOP
      BEGIN
         obj_name_ := Get_Rec_.object_name;
         obj_type_ := Get_Rec_.object_type;
         IF (obj_type_ = 'FUNCTION') THEN
            str_run_ := 'ALTER FUNCTION ' || obj_name_ || ' COMPILE';
         ELSIF (obj_type_ = 'JAVA SOURCE') THEN
            str_run_ := 'ALTER JAVA SOURCE "' || obj_name_ || '"
COMPILE';
         ELSIF (obj_type_ = 'JAVA CLASS') THEN
            str_run_ := 'ALTER JAVA CLASS "' || obj_name_ || '"
RESOLVE';
         ELSIF (obj_type_ = 'PACKAGE') THEN
            str_run_ := 'ALTER PACKAGE ' || obj_name_ || ' COMPILE';
         ELSIF (obj_type_ = 'PACKAGE BODY') THEN
            str_run_ := 'ALTER PACKAGE ' || obj_name_ || ' COMPILE
BODY';
         ELSIF (obj_type_ = 'PROCEDURE') THEN
            str_run_ := 'ALTER PROCEDURE ' || obj_name_ || ' COMPILE';
         ELSIF (obj_type_ = 'TRIGGER') THEN
            str_run_ := 'ALTER TRIGGER ' || obj_name_ || ' COMPILE';

         ELSIF (obj_type_ = 'VIEW') THEN
            str_run_ := 'ALTER VIEW ' || obj_name_ || ' COMPILE';
         ELSIF (obj_type_ = 'MATERIALIZED VIEW') THEN
            str_run_ := 'ALTER MATERIALIZED VIEW ' || obj_name_ || '
COMPILE';
         ELSIF (obj_type_ = 'DIMENSION') THEN
            str_run_ := 'ALTER DIMENSION ' || obj_name_ || ' COMPILE';
         ELSIF (obj_type_ = 'TYPE') THEN
            str_run_ := 'ALTER TYPE ' || obj_name_ || ' COMPILE';
         END IF;
         --
         cid_ := DBMS_SQL.OPEN_CURSOR;
         DBMS_SQL.PARSE(cid_, str_run_, DBMS_SQL.NATIVE);
         ret_ := DBMS_SQL.EXECUTE(cid_);
         DBMS_SQL.CLOSE_CURSOR(cid_);
      EXCEPTION
         WHEN OTHERS THEN
            BEGIN
               IF (DBMS_SQL.IS_OPEN(cid_)) THEN
                  DBMS_SQL.CLOSE_CURSOR(cid_);
               END IF;
            END;
      END;

   END LOOP; 
END; 

Source:
http://www.orafaq.com/usenet/comp.databases.oracle.misc/2005/02/15/0382.htmy