While there are a huge number of music and video web sites that provide content for download, there are also plenty of sites that stream content. Grabbing streaming content is possible, but in order to do so you need to discover the URL of the streaming files - and that can be very difficult. But that's where URL Snooper comes in.
Just launch the program (it's portable, no installation required) and it will immediately begin scanning your network for streaming URLs, displaying them in a simple table. Right-clicking an address displays an option to copy the address to the clipboard, ready for use in whatever download or playback tool you might have installed.
In our tests, the program didn't work on YouTube, at least not reliably. But then there are already a host of YouTube download services and tools available, so perhaps that's not such a big issue. And if we went elsewhere - Apple's Trailer site, say - the results were much better.
If you do have problems, though, URL Snooper does have extra tools which can help. Click File > Advanced Mode and you're able to filter captured URLs by protocol or key word, as well as defining your preferred network card, sniffing engine and more.