Some tips for hacking/debugging the applets:

1) The Panel Applet Writer's Reference Manual, including the PanelApplet
   library documentation, can be found at 
   http://developer.gnome.org/doc/API/2.0/panel-applet/libpanel-applet.html,
   or in gnome-panel/doc/reference/panel-applet (source). It is not
   completely up to date, but it covers the basics of writing an applet.

2) Look at the other applet implementations. One of the simpler applets is
   the fish applet, which lives in gnome-panel/applets/fish.

3) Read the article about debugging GNOME Applets at 
   http://www.davyd.id.au/articles/debugging-gnome-applets.shtml.
   This article also contains a list of common considerations when developing
   applets. Please, please read this article, it covers everything you're
   likely to need to know. If you find anything is missing, then contact
   the maintainers.

4) Be weary of static, global variables if you plan to allow the user
   to be able to add multiple instances of the applet. Each instance will
   share the static varible. This is described in the debugging article, under
   "Other considerations".

5) You'd probably want to run the applets from CVS, without nescessarily doing
   the same with all of GNOME. To do this, install the applets from CVS to a
   different prefix than the rest of GNOME, and change your bonobo servers 
   directory to $prefix/lib/bonobo/servers. You'll find the config file by
   running "bonobo-activation-sysconf --config-file-path". Add the directory to
   as an <item> at the top of <searchpath>. Log out, run bonobo-slay and make
   sure no bonobo processes are running. When you log in again, your applets
   should be running from the new prefix.
   Running single applets from CVS is described further in Davyd's debugging
   article.
