World Population Monitor is a free Windows gadget to keep track of world population. It installs as a Windows gadget in sidebar of Windows 7, and shows you world population in real time. The population data is pulled from Census.gov.
This world population monitor is an interesting software just to see how world population is increasing day by day. The data is of course not completely accurate, but a close approximation of world population at any time.
This gadget comes with some customization options as well. You can change the refresh frequency (default is once per minute, can be changed to once per several minutes). Apart from that, background color, title color, and more. And finally, you can change the size of the gadget.
Frankly, I am not sure why would I use this gadget; but I am sure this would come handy at public displays, like, hospitals, billboards, etc. If you know of some alternate use, do let me know in comments.
Download World Population monitor free.
Also check out Rainmeter.