I think this is not relevant in GNOME 3, which no longer has applets. Instead, you write extensions. There are multiple simple examples at <a href="http://blog.fpmurphy.com/2011/04/gnome-3-shell-extensions.html" rel="nofollow">http://blog.fpmurphy.com/2011/04/gnome-3-shell-extensions.ht...</a>
Not specific to the GNOME environment, but some people might want to check out dzen if they are interested in piping CLI commands to their desktop.<p><a href="http://sites.google.com/site/gotmor/dzen" rel="nofollow">http://sites.google.com/site/gotmor/dzen</a>