IPSwap is a modified version of Chris Knox's IP Switcher. Like the original, this Widget allows you to quickly switch between 3 preset static IP configurations and DHCP. Unlike the original, this one automatically detects all of your installed network adapters and displays it as a list along with its currently-assigned IP. Just select which adapter to adjust by clicking on the adapter name, then hit one of the four buttons to assign one of the presets to the selected adapter.
All configurations requests are run in the background, so you should not lose interactivity with the Widget even while its reconfiguring your network settings. Lastly, this Widget has a small screen footprint - you can tuck it away elsewhere when you don't need it. This version is the first release on CNET Download.com.