I've tried searching the Ubuntu forums, the Gnome wiki and just using Google, but I've not been able to find a list of Gnome applets. You see the ones made available on installation when you right click on the panel and choose Add, but there are lots of other ones out there. It's just difficult to find any sort of list--eg., using an old iMac keyboard where there is no indication of the status of the numlock key, it's nice to have the status of numlock shown on the panel and yes, there's a little applet that does that. You just have to find it. There may be some others out there that I would like, but I don't even know that I'd want one until I see it described.
What gnome-applets are available
Archived thread 100148 from Desktop Environments. Markdown source: Desktop_Environments/thread_100148_What_gnome-applets_are_available.md
You can try going to www.gnomefiles.org and entering 'applet' in the search field. This netted me approx. 65 entries.
That's the place. Thank you.