Start Screen Unlimited Lite is a free tool which provides various ways to customise the desktop.
You can add custom menus, for instance. An internet search bar, with your choice of search engine. Digital clocks, maybe a stopwatch, power shortcuts, easy user switching, status panels and more.
The free Lite version is limited to personal use only, but has pretty much all the functionality you could need or want. A Deluxe version removes this restriction, adds 3D menus and promises early access to future features.
There's nothing here you can't do better with other desktop extensions, but if you're looking for a starter collection of gadgets then Start Screen Unlimited may be useful.