If you haven’t yet found the GUI Builder feature in Netbeans 5.5 (where have you been?), this feature (previously known as ‘Matisse’), makes it incredibly easy to create pretty good looking user interfaces in Java relatively simply.
java.sun.com have a great article on their site walking through the steps involved in building a UI with Netbeans 5.5. It’s well worth a look if you haven’t seen or used this feature yet.