Vik who works for one of the internal Oracle development teams and blogs at http://adfjsf.blogspot.com/ created two useful extensions for JDeveloper 11g.
One of them allows you to quickly create a zip file containing the workspace you are working on, and the other one shows you the recent items from your RSS feed inside your JDeveloper status bar.
Check them out through the Help->Check for Updates or from the extension exchange.
(if you don't know which RSS feed to use - I would suggest the JDeveloper blogs/how-to aggregated RSS feed : http://www.connotea.org/rss/user/jdeveloper
If you've developed an extension that you think people would like also - drop me a line and I can help you get it published on the extension exchange.
And if you never tried extension development before then I think this weekend will be a great time to try it.
The resources to get you started are here.