Pipes is an interactive feed aggregator and manipulator. Using Pipes, you can create feeds that are more powerful, useful and relevant.
Actually Y! Pipes is tool which gives you ability to create your own web space using variety of different online (web) services, and, at the same time, you don't need to have any programming knowledge or skills, only by using its development interface.
You "just" need to have an idea, to know who you should ask for information and to assemble it into your own unique product.
Like a shoe making process: You don't need to be a lace manufacturer nor having a sewing machine, you "just" need to have an idea how the shoe have to look like and have a pencil to sketch it.
Idea is you, public web services are materials (leather, rubber, etc) and Y! Pipes will be your glue (sewing machine) which will assemble all that.
Yahoo! Launches Pipes (TechCrunch - Nik Cubrilovic)
Yahoo! Pipes: The Modules For Building Pipes (O'Reilly Radar)
Yahoo Pipes (Anil Dash)