If you're interested in discussing Deskbar-Applet, consider subscribing to the Deskbar-Applet mailing list. Discuss Deskbar-Applet with other users in real-time in #deskbar on irc.gimp.net.
Deskbar-Applet bugs are tracked using GNOME Bugzilla.
Also, please try to test your bug against the latest development version, first. Your problem may already be fixed!
If you want to help improving Deskbar-Applet a good starting point are bugs tagged with gnome-love or the Roadmap for the next release.
If you want to write your own plugins for Deskbar-Applet read the guide Writing new-style modules for Deskbar-Applet.
All you have to do is go to preferences and drag your module file on the list of modules. That's it! You should then be able to activate your module in Deskbar-Applet's preferences.
Deskbar-Applet sources can be found from Gnome Git, in the "deskbar-applet" module. Also, you can browse the latest sources online.
$ git clone git://git.gnome.org/deskbar-applet $ cd deskbar-applet $ ./autogen.sh --prefix=/usr $ make # make install (as root)