OK got it, now how do I install it...I haven't worked much with tar files.
Firstly, you will have to have gDesklets installed. You can get it in Synaptic. Get both packages there e.g. gDesklets / Data. GDesklets-Data has a bunch of cool eye-candy Desklets. There's where I got the MAC OSX-like clock.
Some of the Desklets never seemed to work for me, and I assume they are abandoned packages. Therefore, I found the un-official gDeklets archive where I got GoodWeather.
At any rate, launch gDesklets from your menu. You'll see it launch to your Taskbar, and also you'll get a window (Shell) with a host of categories. You can play around with these, and see if you one or two are useful to you.
To install GoodWeather, click File, then chose Install Package. That will launch your Directory, then find where you put the GoodWeather tar.gz package and install it. You should see it land on the right side window of the shell. Double click-it, and it will land on your Desktop.
Now, to get your local weather you need to configure it. Right click it, click configure. You'll need to use your location code. Here in the US just use your zip code.
Your Desklets won't populate your Desktop when you re-boot, but you can change that by adding GDesklets to Sessions. Click New, call it GDesklets, then add /usr/bin/gdesklets to the second line. When you re-boot that GDesklets should appear.
That should do it. You'll have endless hours of fun!