For this purpose I started the APEX Plug-Ins group on linkedIn:
This group is for Oracle Application Express (APEX) enthusiasts with the focus on APEX Plug-Ins. The purpose is to share knowledge, tips & tricks and keep each other informed about all the Plug-Ins out there.
We think it is about time to gather ideas for Plug-Ins (using this cool collaboration tool). So don't be shy, start discussions and add your ideas about the Plug-Ins you think you could use (or even create yourself !) or are just very cool....