One of the best new features of APEX 4.0 is the extensible plugin architecture. You will be able to create your own item and region types as well as custom dynamic actions (javascript enabled actions on the browser). You'll be able to add these plugins right in to the builder so they are available to all of your developers. You will be able to share (or even sell) these with the APEX community. This is big.

To get you started the fine folks at ODTUG are going to build five fantastic plugins and give them away to anyone who attends Kaleidoscope 2010. You can check out the details here.

The trick to writing a great plugin is to have a great idea. I'll have some input into the five plugins. If there is an APEX item type, region type or dynamic action that you think should be there but isn't, please leave me a comment and let me know.