I was wondering if we can use a third party program, besides "Network and Sharing Center," to find WiFi networks.
Is there a popular and recommended application for Windows 7 that finds WiFi networks?
I would say that NetStumbler is the most popular. It does not officially support Windows 7 (Thank you to paradroid for pointing that out), however I did find a site that shows how to configure it to make it work with Windows 7, and it will hopefully work for you.
This one is also very popular, and pretty well reviewed.