Why not write one of your own? You might have a utility that you use all the time or some functionality that would make your daily tasks easier.
Kris Rice has a few entries on his blog on writing extensions, so take a look there and see if there is something that might trigger an idea or offer some advice. Of course you can also take a look at the extensions written by the JDeveloper team and user-base, as their exchange has been running for a few releases now.
Here are the links to Kris's extension entries:
- SQL Developer Extensions and Eclipse (3 May)
- XMLTypes, Excel and an Example Extension (6 March)
- Enhanced Excel and Save Snippets (8 March)
- Forgotten datatypes (15 Feb)
- Forgotten datatypes part 2.... (16 Feb)
...and let me know if there is anything you've written that we can add to the site.