Right-click on an empty space in the Panel, choose Add Applet to Panel, then look for Desktop Pager.
Hope that helps.
OS: Kubuntu 6.06 LTS (Dapper Drake) | KDE 3.5.3
Computer Specs: AMD Sempron 2200 1.5Ghz | VIA KM266 Pro 8235 chipset | nVidia GeForce MX 4000 128MB DDR-RAM 32-bit AGP 8x