A quick heads-up to say that the source code for my Growl D-Bus daemon is up since yesterday evening, enabling you to see Growl network notifications on your Gnome desktop.
Coupled with the Growl relay and Avahi (to announce your Linux box as a Growl-enabled box), it's a pretty nice way to have all sorts of notifications visible to all the computers on your LAN, regardless of whether they run Mac OS X or Linux (a Windows version that uses the standard notification bubbles has been on my mind for ages, but realistically I will not be getting around to it anytime soon).
For instance, I have my web server send me occasional reports on load, Referrers, etc.:
[Apache+PHP] -> [home router] -> [Mac mini] -(relay to all machines)-> [Me]
...and a few other local scripts (like an ADSL connection status monitor). It's all pretty trivial to set up, and I'm sure a lot of people will find this useful.
Talking about useful, and although I use the AdBlocker XUL extension on Firefox, I've just come across a really good custom CSS to block most advertisements in Safari. Finally, junk-free browsing without weird plugins.