From Synaptic, install gdesklets. Then from the Applications/ Accessories/ menu run gDesklets and double-click the ones you want. Edit the properties to set them up.
Actually, my gdesklets did not run. I had to install an old version of python, python2.5, to make them work in May 2009. Most likely this is fixed by the time you read this.
Don't try to install a weather desklet, they never work. The places that they get their weather from want you to look at their advertisements.
Then enter the System/ Preferences/ Startup Applications menu and press Add. Name: Desklets. Command: gdesklets. This will ensure your desklets will come back to you after the next reboot. Or not. If you have a wide WXGA screen on your laptop and you put the desklets on the far right of the screen, they will disappear when you connect a non-wide monitor. Here today, gone tomorrow. They will return when you take off the monitor.