If your an Oracle APEX developer you will want to try http://apex.oracle.com. We have just upgraded this free service to a close (but not yet) production version of Oracle APEX 5.0. If you already use apex.oracle.com login and validate your applications work as before. If you don't have an account create one; it should take about a minute.
Oracle APEX 5 has a new feature called "Universal Theme". A good way to learn universal theme is to install the "Universal Theme" packaged application. Another good way is install other packaged applications like "P-Track" or "Customer Tracker". These applications will show off more responsive and more elegant user interface then was available in previous versions of Oracle APEX. The packaged applications also come with many plugins which can improve your app dev productivity and data visualization.
Give APEX 5 a spin and let us know what you think; we are listening.