That particular screenshot is using gDesklets. It's very heavily dependant on GNOME. There is also SuperKaramba, similar thing but very heavily dependant on KDE. By dependant, I mean it requires you to have a bunch of libraries for that desktop installed for you to be able to use them. So whatever you use now, stick with the relative one to save installing a bunch of unnecessary crap.
The "alternative" choice is adesklets, it is very basic, only requires Python and Imlib2, both of which are very common packages to have installed.