Microsoft on Friday , a hosted service that enables users to construct mashups with a visual tool. The service, written using its Silverlight browser plug-in, is designed so people don't need to write code. Users can embed widgets, like a photo gallery, within existing sites and share them with others. Popfly, now in alpha testing, also includes an application builder for people who want to build Web sites from scratch but don't want to learn HTML. For an expanded screen shot, click here.